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/test/core/linker/integration_spec.ts

@@ -1976,7 +1976,7 @@ class DoublePipe implements PipeTransform {
 @Injectable()
 class DirectiveEmitingEvent {
   msg: string;
-  event: EventEmitter;
+  event: EventEmitter<any>;
 
   constructor() {
     this.msg = '';
@@ -2002,7 +2002,7 @@ class DirectiveUpdatingHostProperties {
 @Directive({selector: '[update-host-actions]', host: {'@setAttr': 'setAttribute'}})
 @Injectable()
 class DirectiveUpdatingHostActions {
-  setAttr: EventEmitter;
+  setAttr: EventEmitter<any>;
 
   constructor() { this.setAttr = new EventEmitter(); }