More candy from Hush

* We're avoiding mutability a lot in Hush, which would explain some of
  the seemingly trivial categories on dictionaries.

* The usefulness of each of these in a generic sense is open to debate
  if the reviewer considers these to be too specific to Hush.
Isn't NSDictionary a consortium of classes and an isKindOfClass check risky?

You should use conformsToProtocol:@protocol(NSFastEnumeration) and simply do a for-in loop with recursive call to the same method instead of create two methods that essentially do the same thing.