refactor(EventEmitter): rename .next() to .emit()

BREAKING CHANGE:

EventEmitter#next(value) is deprecated, use EventEmitter#emit(value)
instead.

Closes #4287

Closes #5302

modules/angular2/test/common/forms/model_spec.ts

@@ -37,7 +37,7 @@ export function main() {
 
   function asyncValidatorReturningObservable(c) {
     var e = new EventEmitter();
-    PromiseWrapper.scheduleMicrotask(() => ObservableWrapper.callNext(e, {"async": true}));
+    PromiseWrapper.scheduleMicrotask(() => ObservableWrapper.callEmit(e, {"async": true}));
     return e;
   }