Name output sourcemaps after the output file with its extension. (#99)

Author: stevegeek

lib/install/webpack/webpack.config.js

@@ -9,7 +9,7 @@ module.exports = {
   },
   output: {
     filename: "[name].js",
-    sourceMapFilename: "[name].js.map",
+    sourceMapFilename: "[file].map",
     path: path.resolve(__dirname, "app/assets/builds"),
   },
   plugins: [