Fix serve:prod styling issues

Author: Sebastian Florek

package.json

@@ -48,6 +48,7 @@
     "gulp-useref": "~3.0.4",
     "gulp-util": "~3.0.7",
     "gulp-watch": "~4.3.5",
+    "html-minifier": "~1.2.0",
     "isparta": "~4.0.0",
     "karma": "0.13.19",
     "karma-browserify": "~5.0.1",