Implement filter and filterWithKey.
Merge pull request #17 from RamsesDeNorre/filter

Implement filter and filterWithKey.
Fix imports
A little reorganizing of filterWithKey
implemented insertWithKey and insertWith

--HG--
extra : rebase_source : f023e606e25ed4a43417b24a09ce2bf10497354e
extra : amend_source : 4651bb5169452f93061b3d2e39340480b50cff54
extra : histedit_source : e23239ce3991c3f2152fb48445d37e86c4e6a810%2C180950865f61f834133223ba82549229c5173620
Fix 80-column issue
Make commit expectations clearer
Implement Min/Max view functions.
Implement updateMin, updateMax and equivalent withKey functions.
Rewrite deleteMin, deleteMax in terms of updateExtremity.
Add a test for null

Adapted and simplified from a pull request by Ramses de Norre.
Fix deleteFindMin
Fix deleteFindMax
Small improvements to the test code.
implement updateWithKey and rewrite delete to use this
remove old delete function and benchmarks
Merge pull request #20 from bcdarwin/master

implement updateWithKey and rewrite delete to use this
Merge