Add an asynchronous cache, separating out the logic for the caches. Add options for changing them. Both caches dump based on time
Merge branch 'develop' of github.com:twitter/summingbird into feature/branchF
Make cleanup return a future[Unit] for the async caches
use toSeq instead of trimTo(0)
Add in two new options for the MultiTriggerCache:

High memory water mark when to flush

and when to crush down a value
Address review comments
Review comments
Added comments
Use some good observations from comments to simplify
Review comments
use breakout
Merge pull request #396 from twitter/feature/branchF

Pluggable caches in FinalFlatMap