[BUGFIX release] don't load "app" code when loading globals files

The code that gets compiled for the globals build is in a closure with
its own instance of `loader.js`, so the entries for ember-data don't end
up in ember-cli's instance of `loader.js`. The ember-data code does
include shims that end up in the app's instance of loader.js, so we
exclude the app code from running in this case.

bower.json

@@ -1,7 +1,7 @@
 {
   "name": "ember-data",
   "dependencies": {
-    "ember": "components/ember#release",
+    "ember": "components/ember#beta",
     "ember-cli-shims": "ember-cli/ember-cli-shims#0.1.0",
     "ember-cli-test-loader": "ember-cli-test-loader#0.1.3",
     "ember-load-initializers": "ember-cli/ember-load-initializers#0.1.5",
@@ -13,6 +13,6 @@
     "qunit": "~1.18.0"
   },
   "resolutions": {
-    "ember": "release"
+    "ember": "beta"
   }
-}
+}

index.js

@@ -64,6 +64,17 @@ module.exports = {
     return path.join(__dirname, 'blueprints');
   },
 
+  treeForApp: function(dir) {
+    if (this._forceBowerUsage) {
+      // Fake an empty broccoli tree
+      return { inputTree: dir, rebuild: function() { return []; } };
+    }
+
+    // this._super.treeForApp is undefined in ember-cli (1.13) for some reason.
+    // TODO: investigate why treeForApp isn't on _super
+    return dir;
+  },
+
   treeForAddon: function(dir) {
     if (this._forceBowerUsage) {
       // Fakes an empty broccoli tree