Create GitHub Actions Workflow

[KarthikRIyer]

#745

This currently builds OTIO for Python 2.7, 3.6 & 3.7, and uploads the C++ build artefacts.

I still need to properly run coverage using tox.

[ssteinbach]

I suspect that if you follow the pattern of the travis.yml and run everything through tox, it might "just work":

https://github.com/PixarAnimationStudios/OpenTimelineIO/blob/992b3c21d851b4ba815bf70fcae6ab9de3e174b0/.travis.yml#L12-L30

[jhodges10]

Great work on this! I was going to start working on it myself, but I see you've already done most of the work.
I'll do my best to review this some night this week and leave some feedback.

[ssteinbach]

@KarthikRIyer did you have a chance to try using tox for this? If you have trouble I can help you over slack get this working. Would love to get this into the mainline!

[KarthikRIyer]

@ssteinbach not yet. I'll give this a try tomorrow and revert back. Currently facing some issues with my laptop.

[KarthikRIyer]

PR updated. Coverage works now:

https://github.com/KarthikRIyer/OpenTimelineIO/actions/runs/214134544

[ssteinbach]

@KarthikRIyer one more dumb question about this -- this doesn't disable the travis runs, correct? It adds in the GitHub actions runs as well? That is what we would want, I think, so we can compare the two before turning travis back off.

[KarthikRIyer]

@ssteinbach this doesn't affect Travis.

[ssteinbach]

This looks great, thanks Karthik!