feat: upgrade to webpack 4

dev/webpack/webpack.dev.js

@@ -1,13 +1,13 @@
 const webpack = require('webpack')
 const merge = require('webpack-merge')
 
-const ExtractTextPlugin = require('extract-text-webpack-plugin')
 const WriteFilePlugin = require('write-file-webpack-plugin')
 const SimpleProgressWebpackPlugin = require('simple-progress-webpack-plugin')
 
 const common = require('./webpack.common.js')
 
 module.exports = merge(common, {
+  mode: 'development',
   entry: {
     client: ['./client/index.js', 'webpack-hot-middleware/client']
   },
@@ -19,9 +19,9 @@ module.exports = merge(common, {
       format: 'compact'
     }),
     new webpack.DefinePlugin({
-      'process.env.NODE_ENV': JSON.stringify('development')
+      'process.env.NODE_ENV': JSON.stringify('development'),
+      '__REACT_DEVTOOLS_GLOBAL_HOOK__': '({ isDisabled: true })'
     }),
-    new ExtractTextPlugin({ disable: true }),
     new WriteFilePlugin(),
     new webpack.HotModuleReplacementPlugin(),
     new webpack.WatchIgnorePlugin([