CI: Setup CI

[zbeekman]

I'd like to help out setting up CI for rescal-snow. Before I start, I wanted to quickly discuss the options. You can of course use more than one, but this can be difficult to maintain.

GitHub Actions CI:

You need to sign up for the GitHub Actions Beta. This is probably my preferred approach since it integrates well with GitHub and you can test on macOS and Linux easily, using docker images, shell scripts, or the official javascript API. I like how slick this is, and this is probably my prefered approach. The downside is that it may take some time before you're added to the Beta program. For me it was quick, but who knows.

Circle CI:

Free tier is easy to use, and responsive, and provides good interactive debugging through SSH. It supports Linux and Windows in the free tier. The payed tier has docker image caching, and macOS support too.

Travis CI:

Old school open source gold standard. It can get bogged down, have cloud hiccups where things just need to be re-run. Documentation kinda stinks, yml config file is a bit quirky but they support macOS and Linux. I also have the most experience with this.

Other alternatives considered

• GitLab-CI: GitLab-CI is pretty great, but to use it on github you'll need to use bring your own worker hardware, and/or do it through GitHub actions
• AppVeyor: Pretty good Windows support, but still awkward a bit buggy and documentation isn't great. My personal takeaway is don't use this unless you want/need windows support (and consider Circle-CI as an alternative for that case too).

[zbeekman]

Basically, my recommendation is sign up for GitHub Actions Beta if it sounds good to you. Otherwise, (or while waiting) pick a different CI service and sign up, and then let me know which one you think you like the best. I'll then submit a PR to help implement it.