Add in @autorelease pools to the +(void)load methods so that the iOS 5.x runtime does not complain about autoreleased __NSCFData being leaked.
Fix for crash on load, when running on iOS 5. 

Looking at the docs for 5.0, 5.1, 6.0, and 6.1 for NSValueTransformer, it appears that the method allowsReverseTransformation: should be a class method, not an instance method. It is strange that this bug does not appear on the 5.1 - 6.1 runtimes, and only on the 5.0 runtime, but changing to the class_getClassMethod appears to resolve this issue for iOS 5, and allows running on the simulator.

This change has been tested on iOS 5.0 - 6.1 in the simulator, and on Mountain Lion (The My Mac 64 bit target).
Merge pull request #7 from elc/master

Fix for iOS 5.x devices / simulator complaining about __NSCFData being leaked.