Jc/actions

[jwscook]

Thought you might find this useful - run the tests on ubuntu, mac and windows for v1 and v1.5.

I did this in the process of debugging what turns out to be an unrelated github Actions problem.

[codecov[bot]]

Welcome to Codecov :tada:

Once you merge this PR into your default branch, you're all set! Codecov will compare coverage reports and display results in all future pull requests.

Thanks for integrating Codecov - We've got you covered :open_umbrella:

[timholy]

Can you delete any redundant CI files? .travis.yml and appveyor.yml at least.

Also, for future reference MassInstallAction has a demo script that can be useful for this kind of thing.