Move vnu-jar to devDependencies and remove completely htmlhint.

package.json

@@ -90,7 +90,6 @@
     "cross-env": "^5.0.5",
     "eslint": "^4.2.0",
     "eslint-plugin-compat": "^1.0.4",
-    "htmllint-cli": "^0.0.6",
     "jsunitsaucelabs": "^1.2.0",
     "node-sass": "^4.5.3",
     "nodemon": "^1.11.0",
@@ -111,6 +110,7 @@
     "stylelint-order": "^0.7.0",
     "stylelint-scss": "^2.1.0",
     "uglify-js": "^3.0.24",
+    "vnu-jar": "^17.11.1",
     "workbox-build": "^2.0.1"
   },
   "engines": {