ENH: better docstring and test for warp_coords

skimage/transform/__init__.py

@@ -3,7 +3,7 @@ from .radon_transform import *
 from .finite_radon_transform import *
 from ._project import homography as fast_homography
 from .integral import *
-from ._geometric import (warp, estimate_transform,
+from ._geometric import (warp, warp_coords, estimate_transform,
                          SimilarityTransform, AffineTransform,
                          ProjectiveTransform, PolynomialTransform)
 from ._warps import swirl, homography