Replace Travis with Github Actions

[michel2323]

This largely replaces Travis with Github Actions. It runs

• pkg> test
• the tests that were previously in .travis.yml

Github Actions should be free for public repositories and they allow to do self-hosted runners and run tests with the GPU enabled.

I don't have the permissions to add a runner. Here are the docs: https://docs.github.com/en/free-pro-team@latest/actions/hosting-your-own-runners/adding-self-hosted-runners .

Basically, if you add a runner Github will give you a link to download the client together with a key. This key is important. Maybe you can send the link and the key to me over slack if you like the idea of Github Actions. Our experience with ExaPF, short as it maybe, has been very nice so far.

Edit: A runner is added under "Settings -> Actions -> Self-hosted Runners"

[codecov-commenter]

Codecov Report

Merging #4 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master       #4   +/-   ##
=======================================
  Coverage   92.16%   92.16%           
=======================================
  Files          18       18           
  Lines        2336     2336           
=======================================
  Hits         2153     2153           
  Misses        183      183           

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[sshin23]

Thanks for putting this together. Merging this to master