devtool value based on NODE_ENV env feature added. Fetching NODE_ENV env var's value bug fixed

Author: arpitgo4

webpack.config.js

@@ -5,11 +5,12 @@ const ENTRY_POINTS = [ './src/index' ];
 const DEV_ENTRY_POINTS = ENTRY_POINTS.concat( [ 'webpack-hot-middleware/client' ] );
 
 module.exports = {
-  devtool: 'cheap-module-eval-source-map',
-  entry: process.NODE_ENV === 'production' ? ENTRY_POINTS : DEV_ENTRY_POINTS,
+  devtool: process.env.NODE_ENV === 'production' ? 'cheap-source-map' : 'cheap-module-eval-source-map',
+  entry: process.env.NODE_ENV === 'production' ? ENTRY_POINTS : DEV_ENTRY_POINTS,
   output: {
     path: path.join(__dirname, 'dist'),
     filename: 'bundle.js',
+    sourceMapFilename: 'bundle.map.js',
     publicPath: '/'
   },
   plugins: [