Refactor the unit test for the crop transformation to ensure that it performs an early return when trying to perform unnecessary/impossible crops.
If x and y is 0 and the image is either the same size or smaller than the specified crop, we do/can not perform any actuall work on the image.
Add a feature expectation that the crop transformation returns the same image size when trying to do crops larger than the image.
Merge pull request #217 from androa/issue-216

Solves issue 216 by returning early.