fix(Observable): Subjects no longer wrapped in Subscriber

Observable.subscribe updated to check for instanceof Subject, test added, import order of Subject changed (moved to top) in Rx and KitchenSink to avoid circular dependency issue. closes #825, closes #748

spec/observable-spec.js

@@ -109,6 +109,13 @@ describe('Observable', function () {
       expect(unsubscribeCalled).toBe(true);
     });
 
+    it('should return the given subject when called with a Subject', function () {
+      var source = Observable.of(42)
+      var subject = new Rx.Subject()
+      var subscriber = source.subscribe(subject)
+      expect(subscriber).toBe(subject)
+    })
+
     describe('when called with an anonymous observer', function () {
       it('should accept an anonymous observer with just a next function', function () {
         Observable.of(1).subscribe({
@@ -161,4 +168,4 @@ describe('Observable.create', function () {
     result.subscribe(function () { });
     expect(called).toBe(true);
   });
-});
+});

src/Observable.ts

@@ -89,7 +89,7 @@ export class Observable<T> implements CoreOperators<T>  {
     let subscriber: Subscriber<T>;
 
     if (observerOrNext && typeof observerOrNext === 'object') {
-      if (observerOrNext instanceof Subscriber) {
+      if (observerOrNext instanceof Subscriber || observerOrNext instanceof Subject) {
         subscriber = (<Subscriber<T>> observerOrNext);
       } else {
         subscriber = new Subscriber(<Observer<T>> observerOrNext);

src/Rx.KitchenSink.ts

@@ -1,3 +1,6 @@
+/* tslint:disable:no-unused-variable */
+import {Subject} from './Subject';
+/* tslint:enable:no-unused-variable */
 import {Observable} from './Observable';
 import {CoreOperators} from './CoreOperators';
 import {Scheduler as IScheduler} from './Scheduler';
@@ -125,7 +128,6 @@ import './operator/zip';
 import './operator/zipAll';
 
 /* tslint:disable:no-unused-variable */
-import {Subject} from './Subject';
 import {Subscription} from './Subscription';
 import {Subscriber} from './Subscriber';
 import {AsyncSubject} from './subject/AsyncSubject';

src/Rx.ts

@@ -1,3 +1,9 @@
+/* tslint:disable:no-unused-variable */
+// Subject imported before Observable to bypass circular dependency issue since
+// Subject extends Observable and Observable references Subject in it's
+// definition
+import {Subject} from './Subject';
+/* tslint:enable:no-unused-variable */
 import {Observable} from './Observable';
 
 // statics
@@ -101,7 +107,6 @@ import './operator/zip';
 import './operator/zipAll';
 
 /* tslint:disable:no-unused-variable */
-import {Subject} from './Subject';
 import {Subscription} from './Subscription';
 import {Subscriber} from './Subscriber';
 import {AsyncSubject} from './subject/AsyncSubject';