Implement FantasyLand ChainRec

[safareli]

As of fantasyland/fantasy-land#152 implement ChainRec specification.

MonadRec instance for Either in purescript might be usefull

I would create PR when have time.

[robotlolita]

Thanks :)

I'll probably visit this after the 2.0 release. Tail recursion is something I feel people have particularly missed in Tasks.

[safareli]

Here is implementation for data.task with tests (it's not quite correct as it is not handling cleanup stuff but without that it works well)

[safareli]

Here i have implemented chainRec for IO, Future, Maybe, Either and Identity so we have work to adopt from

[robotlolita]

Thanks for the references :)