Fix unittests that fail with numpy 1.9

This seems to be due to some very subtle changes in array precision,
so I am swapping assert_array_equal for assert_array_almost_equal.

The occurance of failures on a point release is unsettling, but this
at least keeps the tests informative.
Fix Python3 bootstrap arg test
Type safety
Merge pull request #292 from mwaskom/fix_numpy_tests

Fix unittests that fail with numpy 1.9
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