build performance

WIP

• Incremental builds with webpack-dev-server, webpack-dev-middleware, webpack --watch or [[watch: true | node.js API]]
• [[prefetch | http://webpack.github.io/docs/list-of-plugins.html#prefetchplugin]]
• [[noParse | http://webpack.github.io/docs/configuration.html#module-noparse]]
• analyse tool gives hints
• SourceMaps are slow
  • devtool: "eval-source-map"
  • new UglifyJsPlugin({ sourceMap: false })