Add NSUndoManager category with block interface
Update README
Condition for valid redo registration
Add license to files
Merge pull request #46 from Raizlabs/feature/ndonald2/BlockUndoManager

Block-based interface for NSUndoManager
Adding a max image size property
Adding some comments
Switching to compare to CGSizeZero instead of checking width and height
renaming Terribly named variable to something that makes sense
Merge pull request #48 from Raizlabs/feature/arrouse/maxImageSize

Adding a max image size to RZImageCache
- Add license to string categories
- Merge master