diff --git a/wp-includes/js/underscore.js b/wp-includes/js/underscore.js
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+//     Underscore.js 1.8.3
+//     http://underscorejs.org
+//     (c) 2009-2015 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
+//     Underscore may be freely distributed under the MIT license.
+
+(function() {
+
+  // Baseline setup
+  // --------------
+
+  // Establish the root object, `window` in the browser, or `exports` on the server.
+  var root = this;
+
+  // Save the previous value of the `_` variable.
+  var previousUnderscore = root._;
+
+  // Save bytes in the minified (but not gzipped) version:
+  var ArrayProto = Array.prototype, ObjProto = Object.prototype, FuncProto = Function.prototype;
+
+  // Create quick reference variables for speed access to core prototypes.
+  var
+    push             = ArrayProto.push,
+    slice            = ArrayProto.slice,
+    toString         = ObjProto.toString,
+    hasOwnProperty   = ObjProto.hasOwnProperty;
+
+  // All **ECMAScript 5** native function implementations that we hope to use
+  // are declared here.
+  var
+    nativeIsArray      = Array.isArray,
+    nativeKeys         = Object.keys,
+    nativeBind         = FuncProto.bind,
+    nativeCreate       = Object.create;
+
+  // Naked function reference for surrogate-prototype-swapping.
+  var Ctor = function(){};
+
+  // Create a safe reference to the Underscore object for use below.
+  var _ = function(obj) {
+    if (obj instanceof _) return obj;
+    if (!(this instanceof _)) return new _(obj);
+    this._wrapped = obj;
+  };
+
+  // Export the Underscore object for **Node.js**, with
+  // backwards-compatibility for the old `require()` API. If we're in
+  // the browser, add `_` as a global object.
+  if (typeof exports !== 'undefined') {
+    if (typeof module !== 'undefined' && module.exports) {
+      exports = module.exports = _;
+    }
+    exports._ = _;
+  } else {
+    root._ = _;
+  }
+
+  // Current version.
+  _.VERSION = '1.8.3';
+
+  // Internal function that returns an efficient (for current engines) version
+  // of the passed-in callback, to be repeatedly applied in other Underscore
+  // functions.
+  var optimizeCb = function(func, context, argCount) {
+    if (context === void 0) return func;
+    switch (argCount == null ? 3 : argCount) {
+      case 1: return function(value) {
+        return func.call(context, value);
+      };
+      case 2: return function(value, other) {
+        return func.call(context, value, other);
+      };
+      case 3: return function(value, index, collection) {
+        return func.call(context, value, index, collection);
+      };
+      case 4: return function(accumulator, value, index, collection) {
+        return func.call(context, accumulator, value, index, collection);
+      };
+    }
+    return function() {
+      return func.apply(context, arguments);
+    };
+  };
+
+  // A mostly-internal function to generate callbacks that can be applied
+  // to each element in a collection, returning the desired result — either
+  // identity, an arbitrary callback, a property matcher, or a property accessor.
+  var cb = function(value, context, argCount) {
+    if (value == null) return _.identity;
+    if (_.isFunction(value)) return optimizeCb(value, context, argCount);
+    if (_.isObject(value)) return _.matcher(value);
+    return _.property(value);
+  };
+  _.iteratee = function(value, context) {
+    return cb(value, context, Infinity);
+  };
+
+  // An internal function for creating assigner functions.
+  var createAssigner = function(keysFunc, undefinedOnly) {
+    return function(obj) {
+      var length = arguments.length;
+      if (length < 2 || obj == null) return obj;
+      for (var index = 1; index < length; index++) {
+        var source = arguments[index],
+            keys = keysFunc(source),
+            l = keys.length;
+        for (var i = 0; i < l; i++) {
+          var key = keys[i];
+          if (!undefinedOnly || obj[key] === void 0) obj[key] = source[key];
+        }
+      }
+      return obj;
+    };
+  };
+
+  // An internal function for creating a new object that inherits from another.
+  var baseCreate = function(prototype) {
+    if (!_.isObject(prototype)) return {};
+    if (nativeCreate) return nativeCreate(prototype);
+    Ctor.prototype = prototype;
+    var result = new Ctor;
+    Ctor.prototype = null;
+    return result;
+  };
+
+  var property = function(key) {
+    return function(obj) {
+      return obj == null ? void 0 : obj[key];
+    };
+  };
+
+  // Helper for collection methods to determine whether a collection
+  // should be iterated as an array or as an object
+  // Related: http://people.mozilla.org/~jorendorff/es6-draft.html#sec-tolength
+  // Avoids a very nasty iOS 8 JIT bug on ARM-64. #2094
+  var MAX_ARRAY_INDEX = Math.pow(2, 53) - 1;
+  var getLength = property('length');
+  var isArrayLike = function(collection) {
+    var length = getLength(collection);
+    return typeof length == 'number' && length >= 0 && length <= MAX_ARRAY_INDEX;
+  };
+
+  // Collection Functions
+  // --------------------
+
+  // The cornerstone, an `each` implementation, aka `forEach`.
+  // Handles raw objects in addition to array-likes. Treats all
+  // sparse array-likes as if they were dense.
+  _.each = _.forEach = function(obj, iteratee, context) {
+    iteratee = optimizeCb(iteratee, context);
+    var i, length;
+    if (isArrayLike(obj)) {
+      for (i = 0, length = obj.length; i < length; i++) {
+        iteratee(obj[i], i, obj);
+      }
+    } else {
+      var keys = _.keys(obj);
+      for (i = 0, length = keys.length; i < length; i++) {
+        iteratee(obj[keys[i]], keys[i], obj);
+      }
+    }
+    return obj;
+  };
+
+  // Return the results of applying the iteratee to each element.
+  _.map = _.collect = function(obj, iteratee, context) {
+    iteratee = cb(iteratee, context);
+    var keys = !isArrayLike(obj) && _.keys(obj),
+        length = (keys || obj).length,
+        results = Array(length);
+    for (var index = 0; index < length; index++) {
+      var currentKey = keys ? keys[index] : index;
+      results[index] = iteratee(obj[currentKey], currentKey, obj);
+    }
+    return results;
+  };
+
+  // Create a reducing function iterating left or right.
+  function createReduce(dir) {
+    // Optimized iterator function as using arguments.length
+    // in the main function will deoptimize the, see #1991.
+    function iterator(obj, iteratee, memo, keys, index, length) {
+      for (; index >= 0 && index < length; index += dir) {
+        var currentKey = keys ? keys[index] : index;
+        memo = iteratee(memo, obj[currentKey], currentKey, obj);
+      }
+      return memo;
+    }
+
+    return function(obj, iteratee, memo, context) {
+      iteratee = optimizeCb(iteratee, context, 4);
+      var keys = !isArrayLike(obj) && _.keys(obj),
+          length = (keys || obj).length,
+          index = dir > 0 ? 0 : length - 1;
+      // Determine the initial value if none is provided.
+      if (arguments.length < 3) {
+        memo = obj[keys ? keys[index] : index];
+        index += dir;
+      }
+      return iterator(obj, iteratee, memo, keys, index, length);
+    };
+  }
+
+  // **Reduce** builds up a single result from a list of values, aka `inject`,
+  // or `foldl`.
+  _.reduce = _.foldl = _.inject = createReduce(1);
+
+  // The right-associative version of reduce, also known as `foldr`.
+  _.reduceRight = _.foldr = createReduce(-1);
+
+  // Return the first value which passes a truth test. Aliased as `detect`.
+  _.find = _.detect = function(obj, predicate, context) {
+    var key;
+    if (isArrayLike(obj)) {
+      key = _.findIndex(obj, predicate, context);
+    } else {
+      key = _.findKey(obj, predicate, context);
+    }
+    if (key !== void 0 && key !== -1) return obj[key];
+  };
+
+  // Return all the elements that pass a truth test.
+  // Aliased as `select`.
+  _.filter = _.select = function(obj, predicate, context) {
+    var results = [];
+    predicate = cb(predicate, context);
+    _.each(obj, function(value, index, list) {
+      if (predicate(value, index, list)) results.push(value);
+    });
+    return results;
+  };
+
+  // Return all the elements for which a truth test fails.
+  _.reject = function(obj, predicate, context) {
+    return _.filter(obj, _.negate(cb(predicate)), context);
+  };
+
+  // Determine whether all of the elements match a truth test.
+  // Aliased as `all`.
+  _.every = _.all = function(obj, predicate, context) {
+    predicate = cb(predicate, context);
+    var keys = !isArrayLike(obj) && _.keys(obj),
+        length = (keys || obj).length;
+    for (var index = 0; index < length; index++) {
+      var currentKey = keys ? keys[index] : index;
+      if (!predicate(obj[currentKey], currentKey, obj)) return false;
+    }
+    return true;
+  };
+
+  // Determine if at least one element in the object matches a truth test.
+  // Aliased as `any`.
+  _.some = _.any = function(obj, predicate, context) {
+    predicate = cb(predicate, context);
+    var keys = !isArrayLike(obj) && _.keys(obj),
+        length = (keys || obj).length;
+    for (var index = 0; index < length; index++) {
+      var currentKey = keys ? keys[index] : index;
+      if (predicate(obj[currentKey], currentKey, obj)) return true;
+    }
+    return false;
+  };
+
+  // Determine if the array or object contains a given item (using `===`).
+  // Aliased as `includes` and `include`.
+  _.contains = _.includes = _.include = function(obj, item, fromIndex, guard) {
+    if (!isArrayLike(obj)) obj = _.values(obj);
+    if (typeof fromIndex != 'number' || guard) fromIndex = 0;
+    return _.indexOf(obj, item, fromIndex) >= 0;
+  };
+
+  // Invoke a method (with arguments) on every item in a collection.
+  _.invoke = function(obj, method) {
+    var args = slice.call(arguments, 2);
+    var isFunc = _.isFunction(method);
+    return _.map(obj, function(value) {
+      var func = isFunc ? method : value[method];
+      return func == null ? func : func.apply(value, args);
+    });
+  };
+
+  // Convenience version of a common use case of `map`: fetching a property.
+  _.pluck = function(obj, key) {
+    return _.map(obj, _.property(key));
+  };
+
+  // Convenience version of a common use case of `filter`: selecting only objects
+  // containing specific `key:value` pairs.
+  _.where = function(obj, attrs) {
+    return _.filter(obj, _.matcher(attrs));
+  };
+
+  // Convenience version of a common use case of `find`: getting the first object
+  // containing specific `key:value` pairs.
+  _.findWhere = function(obj, attrs) {
+    return _.find(obj, _.matcher(attrs));
+  };
+
+  // Return the maximum element (or element-based computation).
+  _.max = function(obj, iteratee, context) {
+    var result = -Infinity, lastComputed = -Infinity,
+        value, computed;
+    if (iteratee == null && obj != null) {
+      obj = isArrayLike(obj) ? obj : _.values(obj);
+      for (var i = 0, length = obj.length; i < length; i++) {
+        value = obj[i];
+        if (value > result) {
+          result = value;
+        }
+      }
+    } else {
+      iteratee = cb(iteratee, context);
+      _.each(obj, function(value, index, list) {
+        computed = iteratee(value, index, list);
+        if (computed > lastComputed || computed === -Infinity && result === -Infinity) {
+          result = value;
+          lastComputed = computed;
+        }
+      });
+    }
+    return result;
+  };
+
+  // Return the minimum element (or element-based computation).
+  _.min = function(obj, iteratee, context) {
+    var result = Infinity, lastComputed = Infinity,
+        value, computed;
+    if (iteratee == null && obj != null) {
+      obj = isArrayLike(obj) ? obj : _.values(obj);
+      for (var i = 0, length = obj.length; i < length; i++) {
+        value = obj[i];
+        if (value < result) {
+          result = value;
+        }
+      }
+    } else {
+      iteratee = cb(iteratee, context);
+      _.each(obj, function(value, index, list) {
+        computed = iteratee(value, index, list);
+        if (computed < lastComputed || computed === Infinity && result === Infinity) {
+          result = value;
+          lastComputed = computed;
+        }
+      });
+    }
+    return result;
+  };
+
+  // Shuffle a collection, using the modern version of the
+  // [Fisher-Yates shuffle](http://en.wikipedia.org/wiki/Fisher–Yates_shuffle).
+  _.shuffle = function(obj) {
+    var set = isArrayLike(obj) ? obj : _.values(obj);
+    var length = set.length;
+    var shuffled = Array(length);
+    for (var index = 0, rand; index < length; index++) {
+      rand = _.random(0, index);
+      if (rand !== index) shuffled[index] = shuffled[rand];
+      shuffled[rand] = set[index];
+    }
+    return shuffled;
+  };
+
+  // Sample **n** random values from a collection.
+  // If **n** is not specified, returns a single random element.
+  // The internal `guard` argument allows it to work with `map`.
+  _.sample = function(obj, n, guard) {
+    if (n == null || guard) {
+      if (!isArrayLike(obj)) obj = _.values(obj);
+      return obj[_.random(obj.length - 1)];
+    }
+    return _.shuffle(obj).slice(0, Math.max(0, n));
+  };
+
+  // Sort the object's values by a criterion produced by an iteratee.
+  _.sortBy = function(obj, iteratee, context) {
+    iteratee = cb(iteratee, context);
+    return _.pluck(_.map(obj, function(value, index, list) {
+      return {
+        value: value,
+        index: index,
+        criteria: iteratee(value, index, list)
+      };
+    }).sort(function(left, right) {
+      var a = left.criteria;
+      var b = right.criteria;
+      if (a !== b) {
+        if (a > b || a === void 0) return 1;
+        if (a < b || b === void 0) return -1;
+      }
+      return left.index - right.index;
+    }), 'value');
+  };
+
+  // An internal function used for aggregate "group by" operations.
+  var group = function(behavior) {
+    return function(obj, iteratee, context) {
+      var result = {};
+      iteratee = cb(iteratee, context);
+      _.each(obj, function(value, index) {
+        var key = iteratee(value, index, obj);
+        behavior(result, value, key);
+      });
+      return result;
+    };
+  };
+
+  // Groups the object's values by a criterion. Pass either a string attribute
+  // to group by, or a function that returns the criterion.
+  _.groupBy = group(function(result, value, key) {
+    if (_.has(result, key)) result[key].push(value); else result[key] = [value];
+  });
+
+  // Indexes the object's values by a criterion, similar to `groupBy`, but for
+  // when you know that your index values will be unique.
+  _.indexBy = group(function(result, value, key) {
+    result[key] = value;
+  });
+
+  // Counts instances of an object that group by a certain criterion. Pass
+  // either a string attribute to count by, or a function that returns the
+  // criterion.
+  _.countBy = group(function(result, value, key) {
+    if (_.has(result, key)) result[key]++; else result[key] = 1;
+  });
+
+  // Safely create a real, live array from anything iterable.
+  _.toArray = function(obj) {
+    if (!obj) return [];
+    if (_.isArray(obj)) return slice.call(obj);
+    if (isArrayLike(obj)) return _.map(obj, _.identity);
+    return _.values(obj);
+  };
+
+  // Return the number of elements in an object.
+  _.size = function(obj) {
+    if (obj == null) return 0;
+    return isArrayLike(obj) ? obj.length : _.keys(obj).length;
+  };
+
+  // Split a collection into two arrays: one whose elements all satisfy the given
+  // predicate, and one whose elements all do not satisfy the predicate.
+  _.partition = function(obj, predicate, context) {
+    predicate = cb(predicate, context);
+    var pass = [], fail = [];
+    _.each(obj, function(value, key, obj) {
+      (predicate(value, key, obj) ? pass : fail).push(value);
+    });
+    return [pass, fail];
+  };
+
+  // Array Functions
+  // ---------------
+
+  // Get the first element of an array. Passing **n** will return the first N
+  // values in the array. Aliased as `head` and `take`. The **guard** check
+  // allows it to work with `_.map`.
+  _.first = _.head = _.take = function(array, n, guard) {
+    if (array == null) return void 0;
+    if (n == null || guard) return array[0];
+    return _.initial(array, array.length - n);
+  };
+
+  // Returns everything but the last entry of the array. Especially useful on
+  // the arguments object. Passing **n** will return all the values in
+  // the array, excluding the last N.
+  _.initial = function(array, n, guard) {
+    return slice.call(array, 0, Math.max(0, array.length - (n == null || guard ? 1 : n)));
+  };
+
+  // Get the last element of an array. Passing **n** will return the last N
+  // values in the array.
+  _.last = function(array, n, guard) {
+    if (array == null) return void 0;
+    if (n == null || guard) return array[array.length - 1];
+    return _.rest(array, Math.max(0, array.length - n));
+  };
+
+  // Returns everything but the first entry of the array. Aliased as `tail` and `drop`.
+  // Especially useful on the arguments object. Passing an **n** will return
+  // the rest N values in the array.
+  _.rest = _.tail = _.drop = function(array, n, guard) {
+    return slice.call(array, n == null || guard ? 1 : n);
+  };
+
+  // Trim out all falsy values from an array.
+  _.compact = function(array) {
+    return _.filter(array, _.identity);
+  };
+
+  // Internal implementation of a recursive `flatten` function.
+  var flatten = function(input, shallow, strict, startIndex) {
+    var output = [], idx = 0;
+    for (var i = startIndex || 0, length = getLength(input); i < length; i++) {
+      var value = input[i];
+      if (isArrayLike(value) && (_.isArray(value) || _.isArguments(value))) {
+        //flatten current level of array or arguments object
+        if (!shallow) value = flatten(value, shallow, strict);
+        var j = 0, len = value.length;
+        output.length += len;
+        while (j < len) {
+          output[idx++] = value[j++];
+        }
+      } else if (!strict) {
+        output[idx++] = value;
+      }
+    }
+    return output;
+  };
+
+  // Flatten out an array, either recursively (by default), or just one level.
+  _.flatten = function(array, shallow) {
+    return flatten(array, shallow, false);
+  };
+
+  // Return a version of the array that does not contain the specified value(s).
+  _.without = function(array) {
+    return _.difference(array, slice.call(arguments, 1));
+  };
+
+  // Produce a duplicate-free version of the array. If the array has already
+  // been sorted, you have the option of using a faster algorithm.
+  // Aliased as `unique`.
+  _.uniq = _.unique = function(array, isSorted, iteratee, context) {
+    if (!_.isBoolean(isSorted)) {
+      context = iteratee;
+      iteratee = isSorted;
+      isSorted = false;
+    }
+    if (iteratee != null) iteratee = cb(iteratee, context);
+    var result = [];
+    var seen = [];
+    for (var i = 0, length = getLength(array); i < length; i++) {
+      var value = array[i],
+          computed = iteratee ? iteratee(value, i, array) : value;
+      if (isSorted) {
+        if (!i || seen !== computed) result.push(value);
+        seen = computed;
+      } else if (iteratee) {
+        if (!_.contains(seen, computed)) {
+          seen.push(computed);
+          result.push(value);
+        }
+      } else if (!_.contains(result, value)) {
+        result.push(value);
+      }
+    }
+    return result;
+  };
+
+  // Produce an array that contains the union: each distinct element from all of
+  // the passed-in arrays.
+  _.union = function() {
+    return _.uniq(flatten(arguments, true, true));
+  };
+
+  // Produce an array that contains every item shared between all the
+  // passed-in arrays.
+  _.intersection = function(array) {
+    var result = [];
+    var argsLength = arguments.length;
+    for (var i = 0, length = getLength(array); i < length; i++) {
+      var item = array[i];
+      if (_.contains(result, item)) continue;
+      for (var j = 1; j < argsLength; j++) {
+        if (!_.contains(arguments[j], item)) break;
+      }
+      if (j === argsLength) result.push(item);
+    }
+    return result;
+  };
+
+  // Take the difference between one array and a number of other arrays.
+  // Only the elements present in just the first array will remain.
+  _.difference = function(array) {
+    var rest = flatten(arguments, true, true, 1);
+    return _.filter(array, function(value){
+      return !_.contains(rest, value);
+    });
+  };
+
+  // Zip together multiple lists into a single array -- elements that share
+  // an index go together.
+  _.zip = function() {
+    return _.unzip(arguments);
+  };
+
+  // Complement of _.zip. Unzip accepts an array of arrays and groups
+  // each array's elements on shared indices
+  _.unzip = function(array) {
+    var length = array && _.max(array, getLength).length || 0;
+    var result = Array(length);
+
+    for (var index = 0; index < length; index++) {
+      result[index] = _.pluck(array, index);
+    }
+    return result;
+  };
+
+  // Converts lists into objects. Pass either a single array of `[key, value]`
+  // pairs, or two parallel arrays of the same length -- one of keys, and one of
+  // the corresponding values.
+  _.object = function(list, values) {
+    var result = {};
+    for (var i = 0, length = getLength(list); i < length; i++) {
+      if (values) {
+        result[list[i]] = values[i];
+      } else {
+        result[list[i][0]] = list[i][1];
+      }
+    }
+    return result;
+  };
+
+  // Generator function to create the findIndex and findLastIndex functions
+  function createPredicateIndexFinder(dir) {
+    return function(array, predicate, context) {
+      predicate = cb(predicate, context);
+      var length = getLength(array);
+      var index = dir > 0 ? 0 : length - 1;
+      for (; index >= 0 && index < length; index += dir) {
+        if (predicate(array[index], index, array)) return index;
+      }
+      return -1;
+    };
+  }
+
+  // Returns the first index on an array-like that passes a predicate test
+  _.findIndex = createPredicateIndexFinder(1);
+  _.findLastIndex = createPredicateIndexFinder(-1);
+
+  // Use a comparator function to figure out the smallest index at which
+  // an object should be inserted so as to maintain order. Uses binary search.
+  _.sortedIndex = function(array, obj, iteratee, context) {
+    iteratee = cb(iteratee, context, 1);
+    var value = iteratee(obj);
+    var low = 0, high = getLength(array);
+    while (low < high) {
+      var mid = Math.floor((low + high) / 2);
+      if (iteratee(array[mid]) < value) low = mid + 1; else high = mid;
+    }
+    return low;
+  };
+
+  // Generator function to create the indexOf and lastIndexOf functions
+  function createIndexFinder(dir, predicateFind, sortedIndex) {
+    return function(array, item, idx) {
+      var i = 0, length = getLength(array);
+      if (typeof idx == 'number') {
+        if (dir > 0) {
+            i = idx >= 0 ? idx : Math.max(idx + length, i);
+        } else {
+            length = idx >= 0 ? Math.min(idx + 1, length) : idx + length + 1;
+        }
+      } else if (sortedIndex && idx && length) {
+        idx = sortedIndex(array, item);
+        return array[idx] === item ? idx : -1;
+      }
+      if (item !== item) {
+        idx = predicateFind(slice.call(array, i, length), _.isNaN);
+        return idx >= 0 ? idx + i : -1;
+      }
+      for (idx = dir > 0 ? i : length - 1; idx >= 0 && idx < length; idx += dir) {
+        if (array[idx] === item) return idx;
+      }
+      return -1;
+    };
+  }
+
+  // Return the position of the first occurrence of an item in an array,
+  // or -1 if the item is not included in the array.
+  // If the array is large and already in sort order, pass `true`
+  // for **isSorted** to use binary search.
+  _.indexOf = createIndexFinder(1, _.findIndex, _.sortedIndex);
+  _.lastIndexOf = createIndexFinder(-1, _.findLastIndex);
+
+  // Generate an integer Array containing an arithmetic progression. A port of
+  // the native Python `range()` function. See
+  // [the Python documentation](http://docs.python.org/library/functions.html#range).
+  _.range = function(start, stop, step) {
+    if (stop == null) {
+      stop = start || 0;
+      start = 0;
+    }
+    step = step || 1;
+
+    var length = Math.max(Math.ceil((stop - start) / step), 0);
+    var range = Array(length);
+
+    for (var idx = 0; idx < length; idx++, start += step) {
+      range[idx] = start;
+    }
+
+    return range;
+  };
+
+  // Function (ahem) Functions
+  // ------------------
+
+  // Determines whether to execute a function as a constructor
+  // or a normal function with the provided arguments
+  var executeBound = function(sourceFunc, boundFunc, context, callingContext, args) {
+    if (!(callingContext instanceof boundFunc)) return sourceFunc.apply(context, args);
+    var self = baseCreate(sourceFunc.prototype);
+    var result = sourceFunc.apply(self, args);
+    if (_.isObject(result)) return result;
+    return self;
+  };
+
+  // Create a function bound to a given object (assigning `this`, and arguments,
+  // optionally). Delegates to **ECMAScript 5**'s native `Function.bind` if
+  // available.
+  _.bind = function(func, context) {
+    if (nativeBind && func.bind === nativeBind) return nativeBind.apply(func, slice.call(arguments, 1));
+    if (!_.isFunction(func)) throw new TypeError('Bind must be called on a function');
+    var args = slice.call(arguments, 2);
+    var bound = function() {
+      return executeBound(func, bound, context, this, args.concat(slice.call(arguments)));
+    };
+    return bound;
+  };
+
+  // Partially apply a function by creating a version that has had some of its
+  // arguments pre-filled, without changing its dynamic `this` context. _ acts
+  // as a placeholder, allowing any combination of arguments to be pre-filled.
+  _.partial = function(func) {
+    var boundArgs = slice.call(arguments, 1);
+    var bound = function() {
+      var position = 0, length = boundArgs.length;
+      var args = Array(length);
+      for (var i = 0; i < length; i++) {
+        args[i] = boundArgs[i] === _ ? arguments[position++] : boundArgs[i];
+      }
+      while (position < arguments.length) args.push(arguments[position++]);
+      return executeBound(func, bound, this, this, args);
+    };
+    return bound;
+  };
+
+  // Bind a number of an object's methods to that object. Remaining arguments
+  // are the method names to be bound. Useful for ensuring that all callbacks
+  // defined on an object belong to it.
+  _.bindAll = function(obj) {
+    var i, length = arguments.length, key;
+    if (length <= 1) throw new Error('bindAll must be passed function names');
+    for (i = 1; i < length; i++) {
+      key = arguments[i];
+      obj[key] = _.bind(obj[key], obj);
+    }
+    return obj;
+  };
+
+  // Memoize an expensive function by storing its results.
+  _.memoize = function(func, hasher) {
+    var memoize = function(key) {
+      var cache = memoize.cache;
+      var address = '' + (hasher ? hasher.apply(this, arguments) : key);
+      if (!_.has(cache, address)) cache[address] = func.apply(this, arguments);
+      return cache[address];
+    };
+    memoize.cache = {};
+    return memoize;
+  };
+
+  // Delays a function for the given number of milliseconds, and then calls
+  // it with the arguments supplied.
+  _.delay = function(func, wait) {
+    var args = slice.call(arguments, 2);
+    return setTimeout(function(){
+      return func.apply(null, args);
+    }, wait);
+  };
+
+  // Defers a function, scheduling it to run after the current call stack has
+  // cleared.
+  _.defer = _.partial(_.delay, _, 1);
+
+  // Returns a function, that, when invoked, will only be triggered at most once
+  // during a given window of time. Normally, the throttled function will run
+  // as much as it can, without ever going more than once per `wait` duration;
+  // but if you'd like to disable the execution on the leading edge, pass
+  // `{leading: false}`. To disable execution on the trailing edge, ditto.
+  _.throttle = function(func, wait, options) {
+    var context, args, result;
+    var timeout = null;
+    var previous = 0;
+    if (!options) options = {};
+    var later = function() {
+      previous = options.leading === false ? 0 : _.now();
+      timeout = null;
+      result = func.apply(context, args);
+      if (!timeout) context = args = null;
+    };
+    return function() {
+      var now = _.now();
+      if (!previous && options.leading === false) previous = now;
+      var remaining = wait - (now - previous);
+      context = this;
+      args = arguments;
+      if (remaining <= 0 || remaining > wait) {
+        if (timeout) {
+          clearTimeout(timeout);
+          timeout = null;
+        }
+        previous = now;
+        result = func.apply(context, args);
+        if (!timeout) context = args = null;
+      } else if (!timeout && options.trailing !== false) {
+        timeout = setTimeout(later, remaining);
+      }
+      return result;
+    };
+  };
+
+  // Returns a function, that, as long as it continues to be invoked, will not
+  // be triggered. The function will be called after it stops being called for
+  // N milliseconds. If `immediate` is passed, trigger the function on the
+  // leading edge, instead of the trailing.
+  _.debounce = function(func, wait, immediate) {
+    var timeout, args, context, timestamp, result;
+
+    var later = function() {
+      var last = _.now() - timestamp;
+
+      if (last < wait && last >= 0) {
+        timeout = setTimeout(later, wait - last);
+      } else {
+        timeout = null;
+        if (!immediate) {
+          result = func.apply(context, args);
+          if (!timeout) context = args = null;
+        }
+      }
+    };
+
+    return function() {
+      context = this;
+      args = arguments;
+      timestamp = _.now();
+      var callNow = immediate && !timeout;
+      if (!timeout) timeout = setTimeout(later, wait);
+      if (callNow) {
+        result = func.apply(context, args);
+        context = args = null;
+      }
+
+      return result;
+    };
+  };
+
+  // Returns the first function passed as an argument to the second,
+  // allowing you to adjust arguments, run code before and after, and
+  // conditionally execute the original function.
+  _.wrap = function(func, wrapper) {
+    return _.partial(wrapper, func);
+  };
+
+  // Returns a negated version of the passed-in predicate.
+  _.negate = function(predicate) {
+    return function() {
+      return !predicate.apply(this, arguments);
+    };
+  };
+
+  // Returns a function that is the composition of a list of functions, each
+  // consuming the return value of the function that follows.
+  _.compose = function() {
+    var args = arguments;
+    var start = args.length - 1;
+    return function() {
+      var i = start;
+      var result = args[start].apply(this, arguments);
+      while (i--) result = args[i].call(this, result);
+      return result;
+    };
+  };
+
+  // Returns a function that will only be executed on and after the Nth call.
+  _.after = function(times, func) {
+    return function() {
+      if (--times < 1) {
+        return func.apply(this, arguments);
+      }
+    };
+  };
+
+  // Returns a function that will only be executed up to (but not including) the Nth call.
+  _.before = function(times, func) {
+    var memo;
+    return function() {
+      if (--times > 0) {
+        memo = func.apply(this, arguments);
+      }
+      if (times <= 1) func = null;
+      return memo;
+    };
+  };
+
+  // Returns a function that will be executed at most one time, no matter how
+  // often you call it. Useful for lazy initialization.
+  _.once = _.partial(_.before, 2);
+
+  // Object Functions
+  // ----------------
+
+  // Keys in IE < 9 that won't be iterated by `for key in ...` and thus missed.
+  var hasEnumBug = !{toString: null}.propertyIsEnumerable('toString');
+  var nonEnumerableProps = ['valueOf', 'isPrototypeOf', 'toString',
+                      'propertyIsEnumerable', 'hasOwnProperty', 'toLocaleString'];
+
+  function collectNonEnumProps(obj, keys) {
+    var nonEnumIdx = nonEnumerableProps.length;
+    var constructor = obj.constructor;
+    var proto = (_.isFunction(constructor) && constructor.prototype) || ObjProto;
+
+    // Constructor is a special case.
+    var prop = 'constructor';
+    if (_.has(obj, prop) && !_.contains(keys, prop)) keys.push(prop);
+
+    while (nonEnumIdx--) {
+      prop = nonEnumerableProps[nonEnumIdx];
+      if (prop in obj && obj[prop] !== proto[prop] && !_.contains(keys, prop)) {
+        keys.push(prop);
+      }
+    }
+  }
+
+  // Retrieve the names of an object's own properties.
+  // Delegates to **ECMAScript 5**'s native `Object.keys`
+  _.keys = function(obj) {
+    if (!_.isObject(obj)) return [];
+    if (nativeKeys) return nativeKeys(obj);
+    var keys = [];
+    for (var key in obj) if (_.has(obj, key)) keys.push(key);
+    // Ahem, IE < 9.
+    if (hasEnumBug) collectNonEnumProps(obj, keys);
+    return keys;
+  };
+
+  // Retrieve all the property names of an object.
+  _.allKeys = function(obj) {
+    if (!_.isObject(obj)) return [];
+    var keys = [];
+    for (var key in obj) keys.push(key);
+    // Ahem, IE < 9.
+    if (hasEnumBug) collectNonEnumProps(obj, keys);
+    return keys;
+  };
+
+  // Retrieve the values of an object's properties.
+  _.values = function(obj) {
+    var keys = _.keys(obj);
+    var length = keys.length;
+    var values = Array(length);
+    for (var i = 0; i < length; i++) {
+      values[i] = obj[keys[i]];
+    }
+    return values;
+  };
+
+  // Returns the results of applying the iteratee to each element of the object
+  // In contrast to _.map it returns an object
+  _.mapObject = function(obj, iteratee, context) {
+    iteratee = cb(iteratee, context);
+    var keys =  _.keys(obj),
+          length = keys.length,
+          results = {},
+          currentKey;
+      for (var index = 0; index < length; index++) {
+        currentKey = keys[index];
+        results[currentKey] = iteratee(obj[currentKey], currentKey, obj);
+      }
+      return results;
+  };
+
+  // Convert an object into a list of `[key, value]` pairs.
+  _.pairs = function(obj) {
+    var keys = _.keys(obj);
+    var length = keys.length;
+    var pairs = Array(length);
+    for (var i = 0; i < length; i++) {
+      pairs[i] = [keys[i], obj[keys[i]]];
+    }
+    return pairs;
+  };
+
+  // Invert the keys and values of an object. The values must be serializable.
+  _.invert = function(obj) {
+    var result = {};
+    var keys = _.keys(obj);
+    for (var i = 0, length = keys.length; i < length; i++) {
+      result[obj[keys[i]]] = keys[i];
+    }
+    return result;
+  };
+
+  // Return a sorted list of the function names available on the object.
+  // Aliased as `methods`
+  _.functions = _.methods = function(obj) {
+    var names = [];
+    for (var key in obj) {
+      if (_.isFunction(obj[key])) names.push(key);
+    }
+    return names.sort();
+  };
+
+  // Extend a given object with all the properties in passed-in object(s).
+  _.extend = createAssigner(_.allKeys);
+
+  // Assigns a given object with all the own properties in the passed-in object(s)
+  // (https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object/assign)
+  _.extendOwn = _.assign = createAssigner(_.keys);
+
+  // Returns the first key on an object that passes a predicate test
+  _.findKey = function(obj, predicate, context) {
+    predicate = cb(predicate, context);
+    var keys = _.keys(obj), key;
+    for (var i = 0, length = keys.length; i < length; i++) {
+      key = keys[i];
+      if (predicate(obj[key], key, obj)) return key;
+    }
+  };
+
+  // Return a copy of the object only containing the whitelisted properties.
+  _.pick = function(object, oiteratee, context) {
+    var result = {}, obj = object, iteratee, keys;
+    if (obj == null) return result;
+    if (_.isFunction(oiteratee)) {
+      keys = _.allKeys(obj);
+      iteratee = optimizeCb(oiteratee, context);
+    } else {
+      keys = flatten(arguments, false, false, 1);
+      iteratee = function(value, key, obj) { return key in obj; };
+      obj = Object(obj);
+    }
+    for (var i = 0, length = keys.length; i < length; i++) {
+      var key = keys[i];
+      var value = obj[key];
+      if (iteratee(value, key, obj)) result[key] = value;
+    }
+    return result;
+  };
+
+   // Return a copy of the object without the blacklisted properties.
+  _.omit = function(obj, iteratee, context) {
+    if (_.isFunction(iteratee)) {
+      iteratee = _.negate(iteratee);
+    } else {
+      var keys = _.map(flatten(arguments, false, false, 1), String);
+      iteratee = function(value, key) {
+        return !_.contains(keys, key);
+      };
+    }
+    return _.pick(obj, iteratee, context);
+  };
+
+  // Fill in a given object with default properties.
+  _.defaults = createAssigner(_.allKeys, true);
+
+  // Creates an object that inherits from the given prototype object.
+  // If additional properties are provided then they will be added to the
+  // created object.
+  _.create = function(prototype, props) {
+    var result = baseCreate(prototype);
+    if (props) _.extendOwn(result, props);
+    return result;
+  };
+
+  // Create a (shallow-cloned) duplicate of an object.
+  _.clone = function(obj) {
+    if (!_.isObject(obj)) return obj;
+    return _.isArray(obj) ? obj.slice() : _.extend({}, obj);
+  };
+
+  // Invokes interceptor with the obj, and then returns obj.
+  // The primary purpose of this method is to "tap into" a method chain, in
+  // order to perform operations on intermediate results within the chain.
+  _.tap = function(obj, interceptor) {
+    interceptor(obj);
+    return obj;
+  };
+
+  // Returns whether an object has a given set of `key:value` pairs.
+  _.isMatch = function(object, attrs) {
+    var keys = _.keys(attrs), length = keys.length;
+    if (object == null) return !length;
+    var obj = Object(object);
+    for (var i = 0; i < length; i++) {
+      var key = keys[i];
+      if (attrs[key] !== obj[key] || !(key in obj)) return false;
+    }
+    return true;
+  };
+
+
+  // Internal recursive comparison function for `isEqual`.
+  var eq = function(a, b, aStack, bStack) {
+    // Identical objects are equal. `0 === -0`, but they aren't identical.
+    // See the [Harmony `egal` proposal](http://wiki.ecmascript.org/doku.php?id=harmony:egal).
+    if (a === b) return a !== 0 || 1 / a === 1 / b;
+    // A strict comparison is necessary because `null == undefined`.
+    if (a == null || b == null) return a === b;
+    // Unwrap any wrapped objects.
+    if (a instanceof _) a = a._wrapped;
+    if (b instanceof _) b = b._wrapped;
+    // Compare `[[Class]]` names.
+    var className = toString.call(a);
+    if (className !== toString.call(b)) return false;
+    switch (className) {
+      // Strings, numbers, regular expressions, dates, and booleans are compared by value.
+      case '[object RegExp]':
+      // RegExps are coerced to strings for comparison (Note: '' + /a/i === '/a/i')
+      case '[object String]':
+        // Primitives and their corresponding object wrappers are equivalent; thus, `"5"` is
+        // equivalent to `new String("5")`.
+        return '' + a === '' + b;
+      case '[object Number]':
+        // `NaN`s are equivalent, but non-reflexive.
+        // Object(NaN) is equivalent to NaN
+        if (+a !== +a) return +b !== +b;
+        // An `egal` comparison is performed for other numeric values.
+        return +a === 0 ? 1 / +a === 1 / b : +a === +b;
+      case '[object Date]':
+      case '[object Boolean]':
+        // Coerce dates and booleans to numeric primitive values. Dates are compared by their
+        // millisecond representations. Note that invalid dates with millisecond representations
+        // of `NaN` are not equivalent.
+        return +a === +b;
+    }
+
+    var areArrays = className === '[object Array]';
+    if (!areArrays) {
+      if (typeof a != 'object' || typeof b != 'object') return false;
+
+      // Objects with different constructors are not equivalent, but `Object`s or `Array`s
+      // from different frames are.
+      var aCtor = a.constructor, bCtor = b.constructor;
+      if (aCtor !== bCtor && !(_.isFunction(aCtor) && aCtor instanceof aCtor &&
+                               _.isFunction(bCtor) && bCtor instanceof bCtor)
+                          && ('constructor' in a && 'constructor' in b)) {
+        return false;
+      }
+    }
+    // Assume equality for cyclic structures. The algorithm for detecting cyclic
+    // structures is adapted from ES 5.1 section 15.12.3, abstract operation `JO`.
+
+    // Initializing stack of traversed objects.
+    // It's done here since we only need them for objects and arrays comparison.
+    aStack = aStack || [];
+    bStack = bStack || [];
+    var length = aStack.length;
+    while (length--) {
+      // Linear search. Performance is inversely proportional to the number of
+      // unique nested structures.
+      if (aStack[length] === a) return bStack[length] === b;
+    }
+
+    // Add the first object to the stack of traversed objects.
+    aStack.push(a);
+    bStack.push(b);
+
+    // Recursively compare objects and arrays.
+    if (areArrays) {
+      // Compare array lengths to determine if a deep comparison is necessary.
+      length = a.length;
+      if (length !== b.length) return false;
+      // Deep compare the contents, ignoring non-numeric properties.
+      while (length--) {
+        if (!eq(a[length], b[length], aStack, bStack)) return false;
+      }
+    } else {
+      // Deep compare objects.
+      var keys = _.keys(a), key;
+      length = keys.length;
+      // Ensure that both objects contain the same number of properties before comparing deep equality.
+      if (_.keys(b).length !== length) return false;
+      while (length--) {
+        // Deep compare each member
+        key = keys[length];
+        if (!(_.has(b, key) && eq(a[key], b[key], aStack, bStack))) return false;
+      }
+    }
+    // Remove the first object from the stack of traversed objects.
+    aStack.pop();
+    bStack.pop();
+    return true;
+  };
+
+  // Perform a deep comparison to check if two objects are equal.
+  _.isEqual = function(a, b) {
+    return eq(a, b);
+  };
+
+  // Is a given array, string, or object empty?
+  // An "empty" object has no enumerable own-properties.
+  _.isEmpty = function(obj) {
+    if (obj == null) return true;
+    if (isArrayLike(obj) && (_.isArray(obj) || _.isString(obj) || _.isArguments(obj))) return obj.length === 0;
+    return _.keys(obj).length === 0;
+  };
+
+  // Is a given value a DOM element?
+  _.isElement = function(obj) {
+    return !!(obj && obj.nodeType === 1);
+  };
+
+  // Is a given value an array?
+  // Delegates to ECMA5's native Array.isArray
+  _.isArray = nativeIsArray || function(obj) {
+    return toString.call(obj) === '[object Array]';
+  };
+
+  // Is a given variable an object?
+  _.isObject = function(obj) {
+    var type = typeof obj;
+    return type === 'function' || type === 'object' && !!obj;
+  };
+
+  // Add some isType methods: isArguments, isFunction, isString, isNumber, isDate, isRegExp, isError.
+  _.each(['Arguments', 'Function', 'String', 'Number', 'Date', 'RegExp', 'Error'], function(name) {
+    _['is' + name] = function(obj) {
+      return toString.call(obj) === '[object ' + name + ']';
+    };
+  });
+
+  // Define a fallback version of the method in browsers (ahem, IE < 9), where
+  // there isn't any inspectable "Arguments" type.
+  if (!_.isArguments(arguments)) {
+    _.isArguments = function(obj) {
+      return _.has(obj, 'callee');
+    };
+  }
+
+  // Optimize `isFunction` if appropriate. Work around some typeof bugs in old v8,
+  // IE 11 (#1621), and in Safari 8 (#1929).
+  if (typeof /./ != 'function' && typeof Int8Array != 'object') {
+    _.isFunction = function(obj) {
+      return typeof obj == 'function' || false;
+    };
+  }
+
+  // Is a given object a finite number?
+  _.isFinite = function(obj) {
+    return isFinite(obj) && !isNaN(parseFloat(obj));
+  };
+
+  // Is the given value `NaN`? (NaN is the only number which does not equal itself).
+  _.isNaN = function(obj) {
+    return _.isNumber(obj) && obj !== +obj;
+  };
+
+  // Is a given value a boolean?
+  _.isBoolean = function(obj) {
+    return obj === true || obj === false || toString.call(obj) === '[object Boolean]';
+  };
+
+  // Is a given value equal to null?
+  _.isNull = function(obj) {
+    return obj === null;
+  };
+
+  // Is a given variable undefined?
+  _.isUndefined = function(obj) {
+    return obj === void 0;
+  };
+
+  // Shortcut function for checking if an object has a given property directly
+  // on itself (in other words, not on a prototype).
+  _.has = function(obj, key) {
+    return obj != null && hasOwnProperty.call(obj, key);
+  };
+
+  // Utility Functions
+  // -----------------
+
+  // Run Underscore.js in *noConflict* mode, returning the `_` variable to its
+  // previous owner. Returns a reference to the Underscore object.
+  _.noConflict = function() {
+    root._ = previousUnderscore;
+    return this;
+  };
+
+  // Keep the identity function around for default iteratees.
+  _.identity = function(value) {
+    return value;
+  };
+
+  // Predicate-generating functions. Often useful outside of Underscore.
+  _.constant = function(value) {
+    return function() {
+      return value;
+    };
+  };
+
+  _.noop = function(){};
+
+  _.property = property;
+
+  // Generates a function for a given object that returns a given property.
+  _.propertyOf = function(obj) {
+    return obj == null ? function(){} : function(key) {
+      return obj[key];
+    };
+  };
+
+  // Returns a predicate for checking whether an object has a given set of
+  // `key:value` pairs.
+  _.matcher = _.matches = function(attrs) {
+    attrs = _.extendOwn({}, attrs);
+    return function(obj) {
+      return _.isMatch(obj, attrs);
+    };
+  };
+
+  // Run a function **n** times.
+  _.times = function(n, iteratee, context) {
+    var accum = Array(Math.max(0, n));
+    iteratee = optimizeCb(iteratee, context, 1);
+    for (var i = 0; i < n; i++) accum[i] = iteratee(i);
+    return accum;
+  };
+
+  // Return a random integer between min and max (inclusive).
+  _.random = function(min, max) {
+    if (max == null) {
+      max = min;
+      min = 0;
+    }
+    return min + Math.floor(Math.random() * (max - min + 1));
+  };
+
+  // A (possibly faster) way to get the current timestamp as an integer.
+  _.now = Date.now || function() {
+    return new Date().getTime();
+  };
+
+   // List of HTML entities for escaping.
+  var escapeMap = {
+    '&': '&amp;',
+    '<': '&lt;',
+    '>': '&gt;',
+    '"': '&quot;',
+    "'": '&#x27;',
+    '`': '&#x60;'
+  };
+  var unescapeMap = _.invert(escapeMap);
+
+  // Functions for escaping and unescaping strings to/from HTML interpolation.
+  var createEscaper = function(map) {
+    var escaper = function(match) {
+      return map[match];
+    };
+    // Regexes for identifying a key that needs to be escaped
+    var source = '(?:' + _.keys(map).join('|') + ')';
+    var testRegexp = RegExp(source);
+    var replaceRegexp = RegExp(source, 'g');
+    return function(string) {
+      string = string == null ? '' : '' + string;
+      return testRegexp.test(string) ? string.replace(replaceRegexp, escaper) : string;
+    };
+  };
+  _.escape = createEscaper(escapeMap);
+  _.unescape = createEscaper(unescapeMap);
+
+  // If the value of the named `property` is a function then invoke it with the
+  // `object` as context; otherwise, return it.
+  _.result = function(object, property, fallback) {
+    var value = object == null ? void 0 : object[property];
+    if (value === void 0) {
+      value = fallback;
+    }
+    return _.isFunction(value) ? value.call(object) : value;
+  };
+
+  // Generate a unique integer id (unique within the entire client session).
+  // Useful for temporary DOM ids.
+  var idCounter = 0;
+  _.uniqueId = function(prefix) {
+    var id = ++idCounter + '';
+    return prefix ? prefix + id : id;
+  };
+
+  // By default, Underscore uses ERB-style template delimiters, change the
+  // following template settings to use alternative delimiters.
+  _.templateSettings = {
+    evaluate    : /<%([\s\S]+?)%>/g,
+    interpolate : /<%=([\s\S]+?)%>/g,
+    escape      : /<%-([\s\S]+?)%>/g
+  };
+
+  // When customizing `templateSettings`, if you don't want to define an
+  // interpolation, evaluation or escaping regex, we need one that is
+  // guaranteed not to match.
+  var noMatch = /(.)^/;
+
+  // Certain characters need to be escaped so that they can be put into a
+  // string literal.
+  var escapes = {
+    "'":      "'",
+    '\\':     '\\',
+    '\r':     'r',
+    '\n':     'n',
+    '\u2028': 'u2028',
+    '\u2029': 'u2029'
+  };
+
+  var escaper = /\\|'|\r|\n|\u2028|\u2029/g;
+
+  var escapeChar = function(match) {
+    return '\\' + escapes[match];
+  };
+
+  // JavaScript micro-templating, similar to John Resig's implementation.
+  // Underscore templating handles arbitrary delimiters, preserves whitespace,
+  // and correctly escapes quotes within interpolated code.
+  // NB: `oldSettings` only exists for backwards compatibility.
+  _.template = function(text, settings, oldSettings) {
+    if (!settings && oldSettings) settings = oldSettings;
+    settings = _.defaults({}, settings, _.templateSettings);
+
+    // Combine delimiters into one regular expression via alternation.
+    var matcher = RegExp([
+      (settings.escape || noMatch).source,
+      (settings.interpolate || noMatch).source,
+      (settings.evaluate || noMatch).source
+    ].join('|') + '|$', 'g');
+
+    // Compile the template source, escaping string literals appropriately.
+    var index = 0;
+    var source = "__p+='";
+    text.replace(matcher, function(match, escape, interpolate, evaluate, offset) {
+      source += text.slice(index, offset).replace(escaper, escapeChar);
+      index = offset + match.length;
+
+      if (escape) {
+        source += "'+\n((__t=(" + escape + "))==null?'':_.escape(__t))+\n'";
+      } else if (interpolate) {
+        source += "'+\n((__t=(" + interpolate + "))==null?'':__t)+\n'";
+      } else if (evaluate) {
+        source += "';\n" + evaluate + "\n__p+='";
+      }
+
+      // Adobe VMs need the match returned to produce the correct offest.
+      return match;
+    });
+    source += "';\n";
+
+    // If a variable is not specified, place data values in local scope.
+    if (!settings.variable) source = 'with(obj||{}){\n' + source + '}\n';
+
+    source = "var __t,__p='',__j=Array.prototype.join," +
+      "print=function(){__p+=__j.call(arguments,'');};\n" +
+      source + 'return __p;\n';
+
+    try {
+      var render = new Function(settings.variable || 'obj', '_', source);
+    } catch (e) {
+      e.source = source;
+      throw e;
+    }
+
+    var template = function(data) {
+      return render.call(this, data, _);
+    };
+
+    // Provide the compiled source as a convenience for precompilation.
+    var argument = settings.variable || 'obj';
+    template.source = 'function(' + argument + '){\n' + source + '}';
+
+    return template;
+  };
+
+  // Add a "chain" function. Start chaining a wrapped Underscore object.
+  _.chain = function(obj) {
+    var instance = _(obj);
+    instance._chain = true;
+    return instance;
+  };
+
+  // OOP
+  // ---------------
+  // If Underscore is called as a function, it returns a wrapped object that
+  // can be used OO-style. This wrapper holds altered versions of all the
+  // underscore functions. Wrapped objects may be chained.
+
+  // Helper function to continue chaining intermediate results.
+  var result = function(instance, obj) {
+    return instance._chain ? _(obj).chain() : obj;
+  };
+
+  // Add your own custom functions to the Underscore object.
+  _.mixin = function(obj) {
+    _.each(_.functions(obj), function(name) {
+      var func = _[name] = obj[name];
+      _.prototype[name] = function() {
+        var args = [this._wrapped];
+        push.apply(args, arguments);
+        return result(this, func.apply(_, args));
+      };
+    });
+  };
+
+  // Add all of the Underscore functions to the wrapper object.
+  _.mixin(_);
+
+  // Add all mutator Array functions to the wrapper.
+  _.each(['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], function(name) {
+    var method = ArrayProto[name];
+    _.prototype[name] = function() {
+      var obj = this._wrapped;
+      method.apply(obj, arguments);
+      if ((name === 'shift' || name === 'splice') && obj.length === 0) delete obj[0];
+      return result(this, obj);
+    };
+  });
+
+  // Add all accessor Array functions to the wrapper.
+  _.each(['concat', 'join', 'slice'], function(name) {
+    var method = ArrayProto[name];
+    _.prototype[name] = function() {
+      return result(this, method.apply(this._wrapped, arguments));
+    };
+  });
+
+  // Extracts the result from a wrapped and chained object.
+  _.prototype.value = function() {
+    return this._wrapped;
+  };
+
+  // Provide unwrapping proxy for some methods used in engine operations
+  // such as arithmetic and JSON stringification.
+  _.prototype.valueOf = _.prototype.toJSON = _.prototype.value;
+
+  _.prototype.toString = function() {
+    return '' + this._wrapped;
+  };
+
+  // AMD registration happens at the end for compatibility with AMD loaders
+  // that may not enforce next-turn semantics on modules. Even though general
+  // practice for AMD registration is to be anonymous, underscore registers
+  // as a named module because, like jQuery, it is a base library that is
+  // popular enough to be bundled in a third party lib, but not be part of
+  // an AMD load request. Those cases could generate an error when an
+  // anonymous define() is called outside of a loader request.
+  if (typeof define === 'function' && define.amd) {
+    define('underscore', [], function() {
+      return _;
+    });
+  }
+}.call(this));
diff --git a/wp-includes/js/underscore.min.js b/wp-includes/js/underscore.min.js
index f01025b7bc..e2b52042eb 100644
--- a/wp-includes/js/underscore.min.js
+++ b/wp-includes/js/underscore.min.js
@@ -1,6 +1 @@
-//     Underscore.js 1.8.3
-//     http://underscorejs.org
-//     (c) 2009-2015 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
-//     Underscore may be freely distributed under the MIT license.
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diff --git a/wp-includes/version.php b/wp-includes/version.php
index a4aa85d998..d59dbb555b 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.1-alpha-44528';
+$wp_version = '5.1-alpha-44529';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.