Move steps done in Travis CI into Github Actions

[AndreiXYZ]

Travis CI and GH Actions are pretty much the same anyway.
Doing everything in GH Actions means one less thing to maintain.

[nsorros]

Jeff response to this was that if it works for now don't worry about it. I do agree that this is one less thing to maintain so maybe we can move the black / flake8 check to travis.

We can also retire them since pre-commit does that for you.