Update to work with Cucumber 4. Fix GitHub selector

[icole]

Thanks very much for creating this demo! It's really helpful to see how to integrate Cucumber.js and TestCafe together.

When running the tests I noticed the GitHub results step was failing. It looks like the DOM structure has changed, so I updated the selector to reflect the change. I also was having some issues with some extensions in my Chrome browser so I set it to incognito to get it to work.

I also noticed this was using Cucumber 2 which is a couple major revisions back. I went ahead and updated to the newest version and made compatibility changes.

Let me know if there is anything that I could change differently.