Add a method to prepare for optimizing FlatMapKeys
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
Add summer to tests, ws changes
refactor HDFSState
Strip named producers from graph
Add an optional parameter to set default parallelism for a storm source
better tests
add comment on defensiveness.
Remove unused
better temp paths
better error messages