Add CI using GitHub Actions

[tmm1]

This will run all the tests for new PRs to ensure there are no regressions

[tmm1]

Hmm, I thought before there was no CI but maybe travis CI was really backed up and didn't report back on my PRs when I was looking...

[coveralls]

Coverage remained the same at 77.156% when pulling b840808420b69842cc469ac176dc45691d61a37d on tmm1:tmm1-patch-1 into 7a46f0bba363761a5bf3e23e67c3a180015cb03c on asticode:master.

[asticode]

I've never used Github actions, therefore out of curiosity, would you say it's "better" than Travis? Why?

[tmm1]

I don't have a preference and feel like all the CI services are interchangeable.

TravisCI has announced that travis-ci.org will be shutting down. It's unclear when that is going to happen, and what steps will be required to move CI to travis-ci.com

I noticed that TravisCI is set up to run coverage as well. I missed that before so that's something that would need to be copied over into the GitHub action.

[aler9]

This has been implemented in 0df190a, therefore this PR can be closed.

[asticode]

👍