ekmett/recursion-schemes — pull request #10 by tel (2014-12-05 19:08:57+00:00)
Title: Added chronomorphisms because Free is available now

Actually, I'm just guessing as to that being the reason they were missing. I stumbled across https://github.com/ekmett/ekmett.github.com/blob/master/haskell/Chronomorphism.hs and wondered why it wasn't on Hackage.