refactor(ChangeDetection): rename AsyncPipe to ObservablePipe

The async pipe in templates will now delegate to both Observable pipe or Promise pipe,
whichever first says it can support the input. Therefore, it's beneficial to disambiguate
the name of the AsyncPipe/AsyncPipeFactory constructors to reflect that these actually
support only Observables.

modules/angular2/test/change_detection/pipes/observable_pipe_spec.js

@@ -3,12 +3,12 @@ import {ddescribe, describe, it, iit, xit, expect, beforeEach, afterEach,
 import {IMPLEMENTS} from 'angular2/src/facade/lang';
 
 import {WrappedValue} from 'angular2/src/change_detection/pipes/pipe';
-import {AsyncPipe} from 'angular2/src/change_detection/pipes/async_pipe';
+import {ObservablePipe} from 'angular2/src/change_detection/pipes/observable_pipe';
 import {ChangeDetectorRef} from 'angular2/src/change_detection/change_detector_ref';
 import {EventEmitter, Observable, ObservableWrapper, PromiseWrapper} from 'angular2/src/facade/async';
 
 export function main() {
-  describe("AsyncPipe", () => {
+  describe("ObservablePipe", () => {
     var emitter;
     var pipe;
     var ref;
@@ -17,7 +17,7 @@ export function main() {
     beforeEach(() => {
       emitter = new EventEmitter();
       ref = new SpyChangeDetectorRef();
-      pipe = new AsyncPipe(ref);
+      pipe = new ObservablePipe(ref);
     });
 
     describe("supports", () => {