chore(gulpfile): add install-example-angular task to install build packages

Use build packages: gulp install-example-angular --build
Restore release packages: gulp install-example-angular
Documented the command in the README

README.md

@@ -121,6 +121,21 @@ Also, there is a script available for Linux and OSX users that will setup the pr
 
 - `./scripts/install.sh`
 
+### Run with current build instead of release packages
+Can switch the `@angular` packages in `~/public/docs/_examples/node_modules` to the current build packages with
+```
+gulp install-example-angular --build
+```
+Restore to RELEASE packages with
+```
+gulp install-example-angular
+```
+>These commands will fail if something is locking any of the packages ... as an IDE often does.
+>
+>The symptom typically is an error trying to `rm -rf node_modules/@angular`.
+>
+>_Solution_: unlock the hold on the package(s). In VS Code, re-load the window (`cmd-P` then enter `>relow`).
+
 
 ## Technology Used
 - Angular 1.x: The production ready version of Angular

gulpfile.js

@@ -451,6 +451,34 @@ gulp.task('remove-example-boilerplate', function() {
   deleteExampleBoilerPlate();
 });
 
+// Npm install Angular libraries into examples/node_modules,
+// either release or current build packages
+// Examples:
+//   gulp install-example-angular --build  // use current build packages
+//   gulp install-example-angular          // restore release packages
+gulp.task('install-example-angular', installExampleAngular);
+
+function installExampleAngular() {
+  var sources;
+  var template;
+  var libs = [
+    'core', 'common', 'compiler',
+    'platform-browser', 'platform-browser-dynamic',
+    'forms', 'http', 'router'];
+
+  // Like: "angular/core-builds" or "@angular/core"
+  sources = libs.map( lib => argv.build ? `angular/${lib}-builds` : `@angular/${lib}`);
+
+  gutil.log(`Installing Angular npm packages from ${argv.build ? 'BUILD' : 'RELEASE'}`);
+
+  var spawnInfo = spawnExt('rm', ['-rf', 'node_modules/@angular'], { cwd: EXAMPLES_PATH});
+  return spawnInfo.promise
+    .then(() =>  {
+      spawnInfo = spawnExt('npm', ['install', ...sources], {cwd: EXAMPLES_PATH});
+      return spawnInfo.promise
+    });
+}
+
 // deletes boilerplate files that were added by copyExampleBoilerplate
 // from locations where an example app is found
 gulp.task('_delete-example-boilerplate', deleteExampleBoilerPlate);