refactor(async): refactor EventEmitter

Refactor EventEmitter and Async Facade to match ES7 Observable semantics, properly use RxJS typedefs, make EventEmitter inherit from RxJS Subject. Closes #4149.

BREAKING CHANGE:
- consumers of EventEmitter no longer need to call .toRx()
- EventEmitter is now generic and requires a type - e.g. `EventEmitter<string>`
- EventEmitter and Observable now use the `.subscribe(generatorOrNext, error, complete)` method instead of `.observer(generator)`
- ObservableWrapper uses `callNext/callError/callComplete` instead of `callNext/callThrow/callReturn`

modules/angular2/src/mock/location_mock.ts

@@ -9,7 +9,7 @@ export class SpyLocation implements Location {
   /** @internal */
   _query: string = '';
   /** @internal */
-  _subject: EventEmitter = new EventEmitter();
+  _subject: EventEmitter<any> = new EventEmitter();
   /** @internal */
   _baseHref: string = '';
 

modules/angular2/src/mock/mock_location_strategy.ts

@@ -8,7 +8,7 @@ export class MockLocationStrategy extends LocationStrategy {
   internalTitle: string = '';
   urlChanges: string[] = [];
   /** @internal */
-  _subject: EventEmitter = new EventEmitter();
+  _subject: EventEmitter<any> = new EventEmitter();
   constructor() { super(); }
 
   simulatePopState(url: string): void {