rjfarmer/mesaplot: Bug fixes

Fixes some bugs

New feature, most plots can now accept an array (instead of just a string) to plot, i.e instead of having xaxis='model_number' you could now do xaxis=m.hist.model_number*2.

Hatching is now available for kippenhan plots instead of just color

New plots include plotNeu (for neutrino luminosities) and L/M

We now have a basic test suite, run with: python3 setup.py test

Kippenhans can now plot in terms of radius instead of just mass, you need mix_relr_regions and burn_relr_regions in your history output