Don't duplicate prefix header in podspec. (Fixes CocoaPods build)

The CocoaPods still doesn't lint properly, due to an upstream problem
with AFNetworking (which is really a bug in CocoaPods). I'm going to
try to get that fixed.
Cleanup parameter behavior.

Two quick things:

 * Align defaults w/ API behavior
 * Handle copying subclasses properly
Run the cleanup code over the entire entity
Merge pull request #27 from berg/master

Fix CocoaPods build