webpack/webpack-dev-server v2.4.0 on GitHub

contentBase: false in combination with the historyApiFallback option threw an error (#791).
Separate logic of adding entry points to the webpack config; this allows alternative implementations like the webpack grunt plugin to use this instead of copying the code (#782).
Update SockJS dependency to fix issue with FireFox constantly refreshing the page (#762).
Show clear error message when --open fails to open the browser (#780).
Allow overlay option to also show compiler warnings (off by default) (#790):

overlay: {
  errors: true,
  warnings: true
}