DEV: Run automated tests in GH actions

[jvkersch]

fixes #9

[jvkersch]

I think this should work -- when I set the event trigger to "push" I get a clean build on Linux and macOS. I'm not sure how to test things when the trigger is set to pull_request. I feel like I'm overlooking something here...

[mdickinson]

The GitHub Actions documentation isn't totally clear here; I think there may be an issue with creating a new workflow from a fork. I was expecting to see an option to approve running the workflow, but that's absent.

[jvkersch]

This PR also removes all Travis configuration -- someone will have to turn off Travis builds at some point.

[mdickinson]

I recreated this using exactly the same commits in PR #11, and the workflow kicked in and passed on that PR. Given that, I'll merge this one and close #11.

The Travis CI run has been removed as a required status check for the master branch protection.

[mdickinson]

LGTM

[mdickinson]

The Travis CI run has been removed as a required status check for the master branch protection.

I've also added the new GitHub Actions runs for macOS and Linux in place of the Travis CI run. Let me know if you want this changed.

[jvkersch]

Thanks @mdickinson, much appreciated! I didn't think about the possibility that a workflow created from a fork wouldn't be picked up automatically, but that makes sense. I'm glad you got things to work.