TODO

   1 - Protocol changes as discussed in the Redis group
   2 - keys expire
   3 - sunion ssub
   4 - write integers in a special way on disk (and on memory?)
   5 - compact types for disk storing of short strings (no 4 bytes overhead!)
   6 - network layer stresser in test in demo
   7 - maxclients directive
   8 - check 'server.dirty' everywere
   9 - replication automated tests