Move CI to github actions

[arlyon]

This is mainly for discussion. I have done some work on arlyon/async-stripe to move to github actions for formatting and tests which I personally prefer over travis as it keeps things on-platform and displays errors inline on the PR. I can prepare a PR for it if that is something we are interested in.

@kestred @seanpianka

Additionally, on my fork, I set it to auto generate schema changes once a week, however that required a bit of work as I wanted to draw a clean seperation between hand-authored and machine-generated code, namely moving all the generated code into a generated subfolder. Happy to merge these changes as well, but just wanted to get the a-ok.

See here for an example: arlyon/async-stripe#45

Cheers!

Alex

[arlyon]

Closing now that async-stripe in the de-facto successor