Trailing whitespace
Add mapMaybe
Generalize mapMaybe to mapFoldable
Merge pull request #95 from quchen/master

mapMaybe for Pipes.Prelude
Fix tiny typo of the tutorial
Merge pull request #97 from hiratara/fix-tiny-typo

Fix tiny typo of the tutorial
Changed `print` to not curry the constraint

I didn't even realize this was legal.  Either way, I would prefer to leave it uncurried.
Polished source code
Removed bidriectional verions of functions
Merge branch 'master' into simpleLift

Merging chances in master before finishing pull request.
Merge branch 'simpleLiftDirect' into simpleLift

Merge removal of bidirectional versions.