Cmocean

Major changes are as follows:

1. New colormaps:
1. rain, topo, tarn, diff
2. new tools:
1. crop and crop_by_percent to modify colormaps

Also address github issues 70, 71, and [another](https://github.com/matplotlib/matplotlib.github.com/issues/26).

The case was persistently not updated and messing things up on Linux machines. Now everything should be consistent and working.

Over time the colormaps have changed a little, including up to this release. The names were previously different as well, but hopefully these won't change anymore.

For japhir to test the 5 fix.