Fixed cropRect size being incorrectly calculated some aspect ratios.
The cropRect is now centered when PECropView.setCropAspectRatio is used to define a crop rect.
Merge pull request #23 from kawanet/work

supports iOS7 translucent navigation bar
add protocol constraint, fix typo
Merge pull request #24 from YuAo/master

Add protocol constraint, fix typo
Update README.md
Update README.md
Merge pull request #19 from rivera-ernesto/pawelkw_enhancements

Pawelkw's enhancements
Update podspec.
Refine drawing grid.
Clean up.
Clean up.
Clean up.
Update podspec.
Update README.md
Constrain button should be hidden when keepingCropAspectRatio = YES