builds failing on travis. Move to rhub?

[tbates]

Hi,
Automated builds on travis were bliss for checking new code and maintaining code against dev versions of OpenMx. But the last successful build is ~2 years old [1].

If the travis can't be fixed, might the free Rhub be worth moving to? A benefit is it supports x86, to arm and MacOS, win, and *nix OSs and stays pretty well in sync with cran build as it's supported by R consortium.

1. https://app.travis-ci.com/github/OpenMx/OpenMx/builds
2. https://r-hub.github.io/rhub

[RMKirkpatrick]

I definitely concur that we need some kind of continuous-integration solution, and that travis is no longer serving our needs there. The last time we discussed this as a team, I believe we settled on adopting Github Actions. But, it's good to know about Rhub, too.

If @mcneale approves, I can soon put some time into reviving our CI.