Merge branch 'release/0.2.3'
Merge branch 'release/0.2.4'
checkpoint state to track batches of progress
small formatting changes
Fix issue with externalizer
Actually add the code.
Merge pull request #316 from twitter/fix-external

Fix issue with externalizer
code review comments, bug fixes and tests
minor formatting
Merge pull request #315 from aniket486/checkpointstate

Initial implementation of checkpoint state
Move Dependants common code to graph
Move to sbt 0.13, sbt-gitflow wasn't compatible. Not in this… needed?
Merge pull request #322 from twitter/feature/sbt-0.13

Move to sbt 0.13, sbt-gitflow wasn't compatible. Not in this… needed?
Merge pull request #321 from twitter/dependant-gen

Move Dependants common code to graph
Merge branch 'develop' of github.com:twitter/summingbird into feature/general_graph

Conflicts:
	summingbird-storm/src/main/scala/com/twitter/summingbird/storm/FinalFlatMapBolt.scala
More generic node interaction
Update tests