Tests pass with `pytest`

Nose, which the package depends on, will no longer be maintained in the future, and has had issue with newer Python versions.

I switched the Gentoo package of Fastaq from nose to pytest, and it appears to work, with all tests passing: https://ppb.chymera.eu/a23c8b.log

I would recommend making the switch here as well, though for our part, it's fully handled downstream. 