Merge pull request #131 from webdriverio/greenkeeper/jest-21.0.0

Update jest to the latest version 🚀

package.json

@@ -45,6 +45,6 @@
     "eslint-config-airbnb-base": "~12.0.0",
     "eslint-plugin-import": "~2.7.0",
     "http-server": "~0.10.0",
-    "jest": "~20.0.4"
+    "jest": "~21.0.0"
   }
 }