mini redis server. Started from forking https://gist.github.com/coleifer/dbbedc287605dcc22990a6e549de9f36

Will add a queue mechanism into this mini redis server.

Also add MULTI/EXEC for transaction (atomic execution)

Version 0.2 TODO: 1, redis-benchmark 2, BGET: block get, and remove once received. 3, SETLENGTH: limit the length of list 4, MULTI/EXEC (client) 5, FLUSHALL: remove all. 6, SELECT: maybe decline this request. User can achieve this by running multiple instances in different ports.