Implement map.
Added a benchmark for map.
Implement mapWithKeys, traverseWithKey, mapAccum, mapAccumWithKey and mapAccumRWithKey
+ Foldable and Traverse Cribit instances

Fix build problems with GHC 7.4 (gh-1)

Thanks to Bob Ippolito for reporting this. Oops!

Relax version constraint on text

format

Mention what a crit-bit tree *is* (thanks, reddit!)

fix formatting + docs
 Implement mapWithKeys, traverseWithKey, mapAccum, mapAccumWithKey and mapAccumRWithKey

Fix build problems with GHC 7.4 (gh-1)

Thanks to Bob Ippolito for reporting this. Oops!

Relax version constraint on text

format