separate .babelrc for prod/dev, add babel-plugin-lodash (#2829)

config/webpack/loaders/babel.js

@@ -1,5 +1,8 @@
 module.exports = {
   test: /\.js(\.erb)?$/,
   exclude: /node_modules/,
-  loader: 'babel-loader'
+  loader: 'babel-loader',
+  options: {
+    forceEnv: process.env.NODE_ENV || 'development'
+  }
 }