Add new color palettes with interactive choosers
Add colorbrewer chooser
Ban jet
Don't trim special colormap values
Add flat_palette, but keep private for now

I think this function would benefit greatly from doing the ramp in a non-RGB
space, but that's not currently implemented.
Add docstrings
Rename choose_cubehelix for consistency
Unit tests and some abstraction
Color input abstraction in blend_palette
Revamp palette docs and add new functions
Fix ordering in choose_cubehelix_palette (closes #296)
Update release notes with new color palette functionality
Merge pull request #286 from mwaskom/more_color_palettes

Add new color palettes with interactive palette widgets