chore(package): update wait-on to version 4.0.2

Closes #116

Author: greenkeeper[bot]

package.json

@@ -45,7 +45,7 @@
     "ol": "5.2.0",
     "phantomjs-prebuilt": "2.1.14",
     "selenium-webdriver": "^3.6.0",
-    "wait-on": "3.1.0"
+    "wait-on": "4.0.2"
   },
   "scripts": {
     "grab": "g4u-grab guide4you-builder guide4you",