added trampolined Future, and Task, which extends Future with error handling
added Catchable typeclass, a context in which exceptions can be caught and thrown
Fix Validation forall description
Merge pull request #297 from ceedubs/validation-forall-doc

Fix Validation forall description
added unit test for Task and made some minor API tweaks
merged
guarding Now(x) flatMap f with More to avoid SOE
add apply to Cokleisli