Merge pull request #329 from pelson/geostationary

Geostationary projection.
Merge pull request #332 from pelson/test_output_directory

Added the posibility that the cwd can hold the results of the cartopy tests.
Fixed image inversion bug with imshow and transformed images.
Updated documentation for imshow.
Added automatic sensible transformed image resolution capability to
imshow.
Supported PIL images.
Fixed failing test.