Wip
Simplify
Fix map coalese bug
tmp
Adds some throttling options too
Make a MergableStore -> Mergeable in the builder api to match the storm one.

Review comments
Fix handling a non-serializable val
Add unittest for UniqueKeyedService.
Fix test note.
Address Ian's notes.
Remove dup file.
Remove un-used import.
Review comment
Add timestamp for testing.
Merge pull request #543 from luckysong/test_uniquekeyed_service

Add unittest for UniqueKeyedService.
Merge pull request #539 from twitter/refactorFFM

Refactors the final flat map a bit
Take part of the changes in
Remove warning
Fix rest of code
Review comments