Add Prelude.Lift benchmarks.
Fix Pipes.Prelude.chain benchmarks.
Merge pull request #64 from archblob/benchmarks

Prelude.Lift benchmarks feedback.
head :: Monad m => Int -> Pipe a a m ()
Tutorial "You shall not pass!" not the one intended
Merge pull request #66 from michaelt/patch-1

head :: Monad m => Int -> Pipe a a m ()
Merge pull request #67 from michaelt/patch-2

Tutorial "You shall not pass!" not the one intended
Updated tutorial and documentation

This incorporates Iain Nicol's suggestions
Added 'for cat' rewrite RULE

This more than doubles performance for utilities that use the 'for cat' idiom