I do not fully understand how the building process works, and have some doubts
on what a "source distribution" should be.
The sdist might be polluted if a "man" directory exists at the project root
when building the distribution.
The inclusion of man pages in the wheel requires it to be built from the sdist,
so it's best to build both at the same time using "python -m build".
Closes#215
Metadata in `setup.cfg` rather than `pyproject.toml` as I'm a bit confused
about `setuptools` support for PEP-621.
Test stuff still in `setup.py`, this needs updating and I'm not satisfied with
the way they are loaded/discovered.
