refactor(async): use ultralight Observable

Closes #5283

modules/angular2/test/core/facade/observable_spec.dart

@@ -0,0 +1,5 @@
+library angular2.test.facade.observable_spec;
+
+main() {
+  //stub to ignore JS Observable specific tests
+}

modules/angular2/test/core/facade/observable_spec.ts

@@ -0,0 +1,63 @@
+import {
+  describe,
+  it,
+  expect,
+  beforeEach,
+  ddescribe,
+  iit,
+  xit,
+  el,
+  SpyObject,
+  AsyncTestCompleter,
+  inject
+} from 'angular2/testing_internal';
+
+import {Observable, Subject, EventEmitter, PromiseWrapper} from 'angular2/src/facade/async';
+
+export function main() {
+  describe("Observable", () => {
+    describe("#core", () => {
+
+      it("should call next with values", inject([AsyncTestCompleter], (async) => {
+
+           let o = new Observable(sink => { sink.next(1); });
+
+           o.subscribe(v => {
+             expect(v).toEqual(1);
+             async.done();
+           });
+
+         }));
+
+      it("should call next and then complete", inject([AsyncTestCompleter], (async) => {
+
+           let o = new Observable(sink => {
+             sink.next(1);
+             sink.complete();
+           });
+           let nexted = false;
+
+           o.subscribe(v => { nexted = true; }, null, () => {
+             expect(nexted).toBe(true);
+             async.done();
+           });
+
+         }));
+
+      it("should call error with errors", inject([AsyncTestCompleter], (async) => {
+
+           let o = new Observable(sink => { sink.error('oh noes!'); });
+
+           o.subscribe(
+               v => {
+
+               },
+               (err) => {
+                 expect(err).toEqual('oh noes!');
+                 async.done();
+               });
+
+         }));
+    });
+  });
+}