Using Promise polyfilling from npm (not bower), as it's dev dependency.

bower.json

@@ -13,8 +13,5 @@
     "/test_runner.js",
     "test",
     "tests"
-  ],
-  "devDependencies": {
-    "amber-compat-es2015": "^0.1.1"
-  }
+  ]
 }

package.json

@@ -34,6 +34,7 @@
     "test:e2e": "(cd external && cd amber-cli && npm test)"
   },
   "devDependencies": {
+    "amber-compat-es2015": "^0.1.4",
     "grunt": "^0.4.0",
     "grunt-contrib-clean": "^0.7.0",
     "grunt-contrib-jshint": "^0.11.0",