CI changes - Github Actions and tox-lsr

We have recently moved our github CI to use Github Actions instead of Travis. Our organization template is here: https://github.com/linux-system-roles/.github

We currently aren’t using any of the more advanced features of Github Actions, as we wanted to achieve parity with Travis as soon as possible.

We have also replaced all of the local scripts used for CI testing with tox-lsr. If you are a system roles developer, you will need to modify your workflow in order to use the new plugin. See README.md for more information.