webpack's css-loader requires Promise polyfill to work

Author: ryu1kn

frontend/package.json

@@ -10,6 +10,7 @@
   },
   "devDependencies": {
     "css-loader": "^0.23.1",
+    "es6-promise": "^3.1.2",
     "eslint": "^2.5.1",
     "style-loader": "^0.13.1",
     "webpack": "^1.12.14"

frontend/webpack.config.js

@@ -1,3 +1,4 @@
+require('es6-promise').polyfill();
 
 module.exports = {
     entry: './entry.js',