Enable hot reload for webpack

[DarthVanger]

For webpack dev server we explicitly set hot: false: https://github.com/DarthVanger/NeuralNotes/blob/master/server/server.js#L8

Would be great to enable hot reload https://webpack.js.org/guides/hot-module-replacement/

Related to https://github.com/DarthVanger/NeuralNotes/issues/84

[dhammma]

https://github.com/gaearon/react-hot-loader