Add RACTuple.tail
Add RACSignal.ap
Basic test for RACSignal.ap
Document precondition of RACTuple.tail
Rename ap to apply. Don't use RACTuple.first.
Fix references to -ap
Comment that the apply block should return an object.
One more reference to -ap
Rename apply to reduceApply
Assert at least 1 arg, reword method summary.
Fix typo.
Reword comment for RACSignal.reduceApply
Remove RACTuple.tail.
Style.
Merge pull request #1228 from jlawton/applicative

Applicative