Update to v5.0.6 & fix tests

While updating the package to v5.0.6 I realized the tests needed a little bit of work to become functional. I ended up having to replicate much of the setup done by Docker Compose - starting two Redis servers and a cluster. Now most of the test suite runs at least, with the exception of the Redis Stack tests and the SSL ones.

With the manual test setup in the check() function, pifpaf is no longer needed.