Polished source code
Added back `Enumerable` instance for `ErrorT` in Haskell98 subset

This just required changing the import scheme to get `ErrorT`/`runErrorT` from
`transformers` instead of the `mtl`
Polished source code
Removing `WriterT` and `RWST` benchmarks

I'm abandoning support for keeping `WriterT` strict in favor of Patrick's
simpler implementation using `distribute`.  The real solution is to fix
`WriterT`.
Version 4.0.0 => 4.0.1
Loosened lower bound on `criterion`
Updated documentation on debugging types
Merge branch 'master' of https://github.com/Gabriel439/Haskell-Pipes-Library
Improved speed of `each`

This was done by writing it directly in terms of `Data.Foldable.foldr`, which
triggers list fusion better.
Fixed haddocks to remove gratuitous qualifiers from type signatures
Added Appendix on quadratic time complexity issues

Related to issue #100.  Hopefully @errge can comment on this to ensure that it
covers most of the topics he wanted to see addressed.
Version 4.0.1 => 4.0.2
Polished code
Replaced 'Void' with internal 'X' type

The purpose of this is to remove the dependency on `void` so that `pipes`
can eventually be incorporated into the Haskell Platform.  Discussions
with Edward indicate that he plans on merging `void` into `base` in
`ghc-7.10`, and when that occurs I will make `X` a type synonym for
`Void`.
Version 4.0.2 => 4.1.0
Loosened upper bound on tests and benchmarks, too
Added 2014 to copyrights
Merge branch 'master' of github.com:Gabriel439/Haskell-Pipes-Library
Added `Pipes.Prelude.sequence`
Polished source code