Switch to Github CI for testing and workflow automation

[Empty2k12]

Right now, we're using Travis as the CI vendor. Ideally, we could use the new Github CI for building, testing and integration testing, all in Docker.
Github CI could also automate things like issue label assignment and the "Status: Merge when CI passes" label.

[Empty2k12]

I am working on this. Progress can be seen here: https://github.com/Empty2k12/rust-github-actions-test