Feature request: integrate with github deployment api

[KnisterPeter]

It would be great to integrate with github deployment / deployment_status apis. I'm not sure if netflify supports this, since I'm not using netlify, but it will work with zeit now.

I guess the right way would be to listen to deployment_status updates until the status is success. In the response of that we have the deployment URL which could then be used to run lighthouse on.

[jakejarvis]

Great idea — this would also solve the race condition problem (#2) I believe. Right now in my personal use I had to put sleep 30 as a step between deployment and Lighthouse to mitigate this. Will look into this as soon as I get a chance, thanks!