Proposal #2316: Add Applicative instances for all MTL Monads

[Isaac Dupree]

Spencer Janssen wrote:
> This proposal is very straightforward: add Applicative instances for all the
> Monads in the MTL.

It's not quite as straightforward as it looks:
If you only need an
instance (Applicative m) => Applicative (Transformer m),
not
instance (Monad m) => Applicative (Transformer m),
will you use the first one?  (I think yes.)

-Isaac