Adds GetBatchingReadableStore
Optimize for multiGet, which would have been costly
rename the GetBatching to MinBatching store
Merge pull request #215 from twitter/batching-readable

Adds GetBatchingReadableStore
fix bug in onFailure enriched mergeable store
Fixes an issue that Future.collect is N^2 on scala Lists
Merge pull request #219 from twitter/fixMergableFutureCollectorPerf

Fixes an issue that Future.collect is N^2 on scala Lists
Merge pull request #218 from singhala/fix_on_failure

fix bug in onFailure enriched mergeable store