Add cartopy and its dependencies

Tested on OS X and Ubuntu.

Includes fix for shapely using the wrong geos version on OS X:

	Assertion failed: (0 != cs), function GEOSCoordSeq_getSize_r, file geos_ts_c.cpp

https://groups.google.com/forum/#!topic/scitools-iris/FkJkxf1vcbA
https://github.com/cfarmer/python_geospatial/issues/3
Add new version of basemap depending on newer geos

Anaconda comes with basemap packaged, but using an older version of
geos which is incompatible with cartopy. This alternative package
lets us install basemap and cartopy side-by-side.
Merge pull request #5 from TheClimateCorporation/add-cartopy

Add cartopy and its dependencies