fixes for lint errors

added missing packages for lint
removed unecessary babel/polyfill

webpack.dev.js

@@ -13,7 +13,7 @@ module.exports = merge(common, {
                 test: /\.js$/,
                 enforce: 'pre',
                 use: ['source-map-loader']
-            },
+            }
         ]
     },
     plugins: [