finetune webpack

[debuggingfuture]

Let's go further after #4

• make use of webpack dev server instead of gulp.watch
• https://github.com/gaearon/react-hot-loader

[jackhftang]

I spent hours this week playing with webpack, but I still cannot figure out the correct workflow. I was able to setup webpack-dev-server, but what if I want to serve other requests? cors?