Contravariant composition, such as with Functor.
Foldable products deriving 1-ness from only one side.
Typo in ProductFoldable1L.
Traverse products deriving 1-ness from only one side.
Typo.
Missed A=>B steps.
Use foldMap1Opt instead.
Also use *opt variants for directional folds.
Missed type params; apply2 not apply.
Silly overrides.
Merge pull request #438

Mixed compositions
use specs2's `beLike` matcher instead of inexhaustive pattern matches