Added `void` to exports
Documented `runListT` better
Increased lower bounds on `mtl`
Version 4.1.2 => 4.1.3
Merge branch 'master' of https://github.com/Gabriel439/Haskell-Pipes-Library

Conflicts:
	pipes.cabal
	src/Pipes.hs
Version 4.1.3 => 4.1.4