feat(facade): add isType method

modules/angular2/src/facade/lang.dart

@@ -25,6 +25,7 @@ bool isPresent(obj) => obj != null;
 bool isBlank(obj) => obj == null;
 bool isString(obj) => obj is String;
 bool isFunction(obj) => obj is Function;
+bool isType(obj) => obj is Type;
 
 String stringify(obj) => obj.toString();
 

modules/angular2/src/facade/lang.es6

@@ -42,6 +42,10 @@ export function isFunction(obj):boolean {
   return typeof obj === "function";
 }
 
+export function isType(obj):boolean {
+  return isFunction(obj);
+}
+
 export function stringify(token):string {
   if (typeof token === 'string') {
     return token;

modules/angular2/src/facade/lang.ts

@@ -48,6 +48,10 @@ export function isFunction(obj): boolean {
   return typeof obj === "function";
 }
 
+export function isType(obj): boolean {
+  return isFunction(obj);
+}
+
 export function stringify(token): string {
   if (typeof token === 'string') {
     return token;