switch uglify to compress:true,mangle:true (#2852)

config/webpack/production.js

@@ -12,22 +12,8 @@ module.exports = merge(sharedConfig, {
 
   plugins: [
     new webpack.optimize.UglifyJsPlugin({
-      compress: {
-        unused: true,
-        evaluate: true,
-        booleans: true,
-        drop_debugger: true,
-        dead_code: true,
-        pure_getters: true,
-        negate_iife: true,
-        conditionals: true,
-        loops: true,
-        cascade: true,
-        keep_fargs: false,
-        warnings: true
-      },
-
-      mangle: false,
+      compress: true,
+      mangle: true,
 
       output: {
         comments: false