Merge pull request #9 from acrosby/temp

PR to add specification of axes when plotting and bbox filter when opening vector dataset with the Fiona interface
GeoSeries can take a keyword argument to set crs.
Streamline kwargs for GeoSeries constructor
Streamline return of geometry column as GeoSeries
Accept crs keyword argument for GeoDataFrame
Preserve crs through geometric operations
Add crs to one of the test geometries
Warning for binary operation on GeoSeries with differing crs
Docstring formatting consistency and additions
Implement passing arguments to series operations
More docstring cleanup and additions
update tests for operations that take arguments
More docstring cleanup
Use numpy.testing to simplify some test assertions
Also fixes almost_equals test
Merge pull request #10 from kjordahl/feature-pandas-fixes

Preserve crs though operations, and some other fixes and cleanup