investigate use of Travis-Ci jobs and stages, etc.

[boneskull]

This is a beta feature on Travis-CI, but we could (potentially) leverage it to make it more obvious what's happening during each build in the matrix.

It may not be worth doing, either. We don't have a bunch of packaging, deployment or artifact generation happening (though we have some).

[Bamieh]

@boneskull Nice! I have been missing this feature on travis, while circleCI has a similar one. I will definitely try it out soon and give feedback/PR.

[outsideris]

I closed this because #3302 has merged.