Updating for iOS7

See this post for an explanation: http://stackoverflow.com/questions/18919459/ios-7-beginupdates-endupdates-inconsistent
Briefly, iOS 7 sometimes returns a NSMutableIndexPath where iOS 6 would return a NSIndexPath. This was causing them to not compare correctly. The solution is to force everything strictly to a NSIndexPath
Merge pull request #2 from mstrater/patch-1

Updating for iOS7