Tree shaking, linting, pre-processed css, and react webpack@^2.1.0-beta.25 config

webpack.config.js

const path = require('path'),
      ExtractTextPlugin = require('extract-text-webpack-plugin'),
      webpack = require('webpack')

const plugins = [
  new ExtractTextPlugin('app.css'),
  new webpack.LoaderOptionsPlugin({
    // test: /\.xxx$/, // may apply this only for some modules
    options: {
      eslint: {
        fix: true,
        test: /\.js$/,
        loader: 'eslint-loader',
        exclude: /node_modules/
      }
    }
  })
]

module.exports = {
  entry: './app/index.js',
  output: {
    filename: 'app.js',
    path: path.join(__dirname, 'public'),
  },

  devtool: 'source-map',

  module: {
    loaders: [
      {
        test: /\.css$/,
        loader: ExtractTextPlugin.extract({
          fallbackLoader: 'style', 
          loader: 'css!postcss'
        })
      },
    ]
  },

  plugins
}