add Foldable
make List use Foldable
Add more folds and a Foldable instance for (Vect n)
Add instance Foldable Maybe
Add traverse_ and sequence_ based on Foldable
Add Traversable and instance for List
Add Traversable instances for Maybe and (Vect n)
Readd toList as working on any Foldable
change traverse on Binder to a Traversable instance
Merge pull request #440 from Melvar/Foldable_Traversable

Add Foldable and Traversable to Prelude