BUG: _series_unary_op() should return a Series, not a GeoSeries
TST: Add a type test to test_area to make sure it returns a Series.
Merge pull request #28 from kjordahl/bug/series_unary_op

BUG: _series_unary_op should return a series
adds various transformation functions - shift, rotate, scale, skew, and a few other minor adjustments/fixes
Merge pull request #29 from cfarmer/transform

Adds various transformation functions - shift, rotate, scale, skew