Remove nosetest and convert tests to pytest

[mplough-kobold]

Previously the Makefile ran tests using nosetests but CI ran tests using pytest. Nose is very old; the last release on PyPI is 1.3.7 from June 2015.

As pytest provides excellent test tooling, this PR transitions tests, documentation, and support tooling to use only pytest. Tests written in unittest.TestCase style have transitioned to use pytest's xunit support.

As tests/test_Scipy.py did include any class-level setup, I transitioned it to parametrized tests as that implementation is much terser.