Migrated Continuous Integration from Travis to GitHub Actions

As some of you may know Travis is no longer free for open source projects. They recently forced everyone to migrate from travis-ci.org to .com, and while doing so they started seriously limiting builds. We have a fixed number of credits and once they are gone they aren't automatically renewed. Instead you have to send them an email to ask for more credits, and you have to do that every time you run out. They can take several weeks to answer and there's no guarantee they'll say yes. They seem to pick high profile projects as a way of promoting the Travis brand, but overall they don't care about open source.

In our case, we used up all the credits in 6 builds, so it's pointless to try to get more. Essentially the "free" Travis plan is there to pretend they support open source when they are clearly forcing everyone to go for their paid package at min $70 a month.

So because of this I have migrated our Continuous Integration to GitHub Actions. As often they have the best offer around for open source projects - it's free, with no conditions, no credits, etc. I don't know if it will last but for now it's a very good opportunity.

Most of our CI is just a Bash script so it was mostly a matter of setting up the GA config and a few env variables. I also took the opportunity to make the Bash script more self-contained so that we can easily switch to a different provider if GitHub changes their T&C too.

Everything seems to work fine so far but if you nothing anything off please let me know.