Fix Ember global deprecation

A minimal fix for #600. We should probably follow through with the
refactor suggested by @rwjblue in #600 but that can be done later.

assets/browser-fetch.js.t

@@ -1,7 +1,7 @@
 (function (originalGlobal) {
-  define('fetch', ['exports'], function(exports) {
+  define('fetch', ['ember', 'exports'], function(Ember, exports) {
     'use strict';
-    var Promise = originalGlobal.Ember.RSVP.Promise;
+    var Promise = Ember.RSVP.Promise;
     var supportProps = [
       'FormData',
       'FileReader',
@@ -49,8 +49,8 @@
       return result;
     }
 
-    if (originalGlobal.Ember.Test) {
-      originalGlobal.Ember.Test.registerWaiter(function() {
+    if (Ember.Test) {
+      Ember.Test.registerWaiter(function() {
         return pending === 0;
       });