Warp.py docstring wins

Still chipping away at #161 

This adds numpy style docstrings to ```warp.py```, deals with some PEP8 line break issues, and adds a couple permutations to the tests for ```transform_geom``` (though still not totally complete as far as unit tests).

No functional code in ```warp.py``` was changed, only changes are formatting (apologies for the quantity of lines involved).