TST: Some tests for pandas methods returning GeoSeries type
BUG: set GeoSeries type in __getitem__ and __getslice__
ENH: Generalize wrapped pandas methods
BUG: Wrap a few more pandas methods that were not returning correct type
TST: Skip tests for methods not yet implemented in GeoPandas
Merge pull request #22 from kjordahl/pandas-methods

Fix slicing and implement some pandas methods