curl/tdd/undefine doesn't undefine modules any more

[unscriptable]

See this gist: http://jsfiddle.net/pPv4v/4/

The problem is the urlCache. The module is still in that cache. We could just add the urlCache to curl's private API so it is accessible to curl/tdd/undefine. However, I've been wanting to remove urlCache for a while now since it seems it's really not the right way to fix the use cases for which it was meant. Unfortunately, I can't remember the use cases, atm. Let me create a new issue for removing urlCache.