test: Moved to tox for cross CI testing.

[ashcrow]

This change moves our testing to use tox instead of "hard coding" the work in travis. This should allow multiple CI systems to easily run the same commands without needing to copy/paste between systems. There still may be some translation (example: we have to download and etcd with wget on Travis while on a Jenkins instance we can probably dnf install) but this still should make it all much simpler.

Thanks to @cgwalters for bringing up the idea of using a central CI script.

[ashcrow]

/cc @jlebon @cooktheryan

With this PR tox can be used to simplify testing.

[jlebon]

:+1: I can simplify the tester once this is merged.

[ashcrow]

ping @cooktheryan