chore(build): Karma watches broccoli output.

This is a prerequisite for switching to TypeScript. We need to remove the Traceur preprocessor
from Karma, so we have the build specified in a single place (broccoli tree def'n).

modules/angular2/src/facade/async.es6

@@ -123,4 +123,4 @@ export class EventEmitter extends Observable {
   return(value) {
     this._subject.onCompleted();
   }
-}
+}

modules/angular2/src/facade/async.ts

@@ -99,4 +99,4 @@ export class EventEmitter extends Observable {
   throw(error) { this._subject.onError(error); }
 
   return (value) { this._subject.onCompleted(); }
-}
+}