Introduce Pytest, Tox, Coverage

Fixes #13.

Still work in progress. Qemu on Travis is very slow :/

The question is whether we actually need Qemu with a real server, or if we can go with mocking one. Then we could get rid of the Qemu setup.
Can you avoid importing the library please, importing the library at install time is a nasty anti-pattern. A plain text file which is read in will be fine for this project.