All present in basemap's cm.
Removed (redundant with GMT cm).
Removed gimp colormaps.
Clean-ups.
Added colormaps as 255x3 csv files.
Removed gmt colormaps.
Some code clean-up and bug fixes.
Added: `get_color()` function to create line plots with a color gradient.
Removed: All GMT (redundant with with basemap) colormaps and GIMP data.
Removed colormaps tests.  Useless as test unless I can compare figure creation.
Added: `wrap_lon` and `map_limits` functions.
Complete re-write of `woa_subset`, now it always return a 4D pandas Panel.