nub
export nub
drop CanNub instance for Vector
Switch to nubBy
Merge branch 'nub' of https://github.com/nikita-volkov/classy-prelude into nub

Conflicts:
	classy-prelude/ClassyPrelude.hs
	classy-prelude/ClassyPrelude/Classes.hs
	classy-prelude/ClassyPrelude/List.hs
	classy-prelude/ClassyPrelude/Vector.hs
More efficient nub