Remove unused imports
Introduce SnapshotWritable for sorting by time/priority and remove PriorityTag
Override NamespacedThriftFactDerived.isTombstone for performance
Use repo.snapshot in PrintFactsSpec
Add kout and vout to Emitter
Add additional date to TwoDifferentDates
Introduce SnapshotPartitions
Add byConcrete combinator in Dictionary
Add Mutator
Remove unused Ordering import from Snapshot
Support snapshot windows
Merge pull request #262 from ambiata/topic/snapshot-windowing

Support snapshot windows