feat(change_detection): added async pipe

modules/angular2/src/facade/async.dart

@@ -37,6 +37,14 @@ class ObservableWrapper {
     return s.listen(onNext, onError: onError, onDone: onComplete, cancelOnError: true);
   }
 
+  static bool isObservable(obs) {
+    return obs is Stream;
+  }
+
+  static void dispose(StreamSubscription s) {
+    s.cancel();
+  }
+
   static void callNext(EventEmitter emitter, value) {
     emitter.add(value);
   }

modules/angular2/src/facade/async.es6

@@ -58,6 +58,14 @@ export class ObservableWrapper {
     return emitter.observer({next: onNext, throw: onThrow, return: onReturn});
   }
 
+  static dispose(subscription:any) {
+    subscription.dispose();
+  }
+
+  static isObservable(obs):boolean {
+    return obs instanceof Observable;
+  }
+
   static callNext(emitter:EventEmitter, value:any) {
     emitter.next(value);
   }

modules/angular2/src/facade/async.ts

@@ -54,6 +54,10 @@ export class ObservableWrapper {
     return emitter.observer({next: onNext, throw: onThrow, return: onReturn});
   }
 
+  static isObservable(obs: any): boolean { return obs instanceof Observable; }
+
+  static dispose(subscription: any) { subscription.dispose(); }
+
   static callNext(emitter: EventEmitter, value: any) { emitter.next(value); }
 
   static callThrow(emitter: EventEmitter, error: any) { emitter.throw(error); }