convert GlyphFunction into an actual function
move big chunk of plotting.py to plotting_helpers.py
fix imports
create all glyph functions explicitly (preparing to add docstrings)
fix some 'invtriangle' leftovers
remove support for 'type' argument to scatter
fix up some typos
add numpydoc and document all glyph functions
add inhertiance diagrams
ditch numpydoc. napoleon looks better online and in docstring and doesn't spit out 6000 spurious warnings
ake more functions conform to google docstring format
restore brewer palette import in plotting.py
override autofunc signatures to be more informative
Merge pull request #337 from ContinuumIO/feature/simpler_plotting_module

simplify plotting module and make auto-documentable