Rename compressor field to compress in UglifyJsPlugin settings (#264)

Author: koistya

config/webpack.config.prod.js

@@ -127,7 +127,7 @@ module.exports = {
     new webpack.optimize.OccurrenceOrderPlugin(),
     new webpack.optimize.DedupePlugin(),
     new webpack.optimize.UglifyJsPlugin({
-      compressor: {
+      compress: {
         screw_ie8: true,
         warnings: false
       },