Added ability to respond to synch queries for Redis

@anpete Both materialized and non-materialized queries now working. 

TODO: add same ability for asynch queries
In general scans can be pretty fast for a small number of elements so there is likely a size under which scans are faster no matter how many times you need to do it. A dictionary also uses more memory. In general we are trying to not pre-optimize. I would replace this with a scan and then add a TODO comment to actually measure & optimize.