Required test/doc packages not included in setup.py

[juliangilbey]

Hi! I'm very excited to try out your excellent looking package!
I notice that setup.py does not have a list of all of the packages required for tests and docs; these should appear in the extras_require argument in the setup() call.
I've found these (so far):
For building documentation (docs): docutils, numpy (though numpy is a dependency of pandas), plotnine, sphinx, sphinx_rtd_theme, nbsphinx, numpydoc
For running tests (test): pytest, numpy (comment as above)

Best wishes, Julian