Fix RuntimeStat's backwards use of WeakHashMap
Use both weak keys and values
Merge pull request #829 from isnotinvain/alexlevenson/RuntimeStatsMemLeak

Fix RuntimeStat's backwards use of WeakHashMap
bump version to 0.9.0rc16
Merge branch 'release/0.9.0rc16' into develop
Adds distinctBy to typed pipe
Fixes small bug, change signature of distinctBy to make the default None reducers nicer. Add test
Strengthen test
Merge pull request #831 from twitter/feature/addDistinctBy

Adds distinctBy to typed pipe
Merge https://github.com/twitter/scalding into develop