Upgrade webpack to v2 and other deps (#8491)

* update to webpack2 and other deps

* fix linting

webpack/config/test.env.js

@@ -2,5 +2,5 @@ const merge = require('webpack-merge');
 const devEnv = require('./dev.env');
 
 module.exports = merge(devEnv, {
-  NODE_ENV: '"testing"',
+  NODE_ENV: '"test"',
 });