A memory store. Needs tweaking to be more consistent with Mongo persistor.
Nasty data structure to keep track of priority for each path
Return the right structure (value and priority fields)
rename mapToJSON to valToJSON
Return values with the right structure.
Update BacksidePersistence test to also test the memory store
Merge pull request #2 from backside/memory_store

A memory store. Needs tweaking to be more consistent with Mongo persistor