- Removed piprot dependency since it's used only with pre-commit and now it's installed inside the hook's virtualenv.

- Stop testing with Docker containers, they're only a good fit for a very limited use (cli applications, not services or system-level) and the speed of testing doesn't justify the work needed.

- Removed `--quiet` from the piprot check to see which packages are out
of date (check still works the same).
- Test on Python 3.5 and not 3.4 because Ansible is tested on 3.5 and
later.

- Build on my supported platforms (some don't have properly working Vagrant boxes so they're allowed to fail).

- Enable free Ansible strategy to allow each host to proceed as fast as it can to help speed up some plays.

accordingly.