Set ExtractTextPlugin.allChunks to true (#1027)

* When using CommonsChunkPlugin and there are extracted chunks (from ExtractTextPlugin.extract) in the commons chunk, allChunks must be set to true
https://github.com/webpack-contrib/extract-text-webpack-plugin

* Explicitly set allChunks to false along with some useful info on codesplit chunks (credit to @LinusBorg)

* Update webpack.prod.conf.js

Author: mgenware

Diff for: template/build/webpack.prod.conf.js

@@ -43,7 +43,11 @@ const webpackConfig = merge(baseWebpackConfig, {
     }),
     // extract css into its own file
     new ExtractTextPlugin({
-      filename: utils.assetsPath('css/[name].[contenthash].css')
+      filename: utils.assetsPath('css/[name].[contenthash].css'),
+      // set the following option to `true` if you want to extract CSS from
+      // codesplit chunks into this main css file as well.
+      // This will result in *all* of your app's CSS being loaded upfront.
+      allChunks: false,
     }),
     // Compress extracted CSS. We are using this plugin so that possible
     // duplicated CSS from different components can be deduped.