Merge branch 'fix-production-assets' into 'master'

Only load istanbul plugin in development mode

See merge request !9261

config/webpack.config.js

@@ -54,7 +54,7 @@ var config = {
         exclude: /(node_modules|vendor\/assets)/,
         loader: 'babel-loader',
         options: {
-          plugins: ['istanbul'],
+          plugins: IS_PRODUCTION ? [] : ['istanbul'],
           presets: [
             ["es2015", {"modules": false}],
             'stage-2'