Took down Cleverbot
Took down Cleverbot

Because Cleverbot is now a paid service, it's no longer possible to maintain cleverbot.
So I just removed it, especially since I never provided the cleverbot in utils.
(the version I used was an async modification of the cleverbot python API,
 and I wasn't sure if I was allowed to post it.)

Ikusaba-san/Chiaki-Nanami