Add example with chained replication

[vbabak]

DB Server (master) <- Replica 1 <- Replica 2
"Replica 1" contains it's own tables and replicated tables from "master".
And "Replica 2" replicates all tables that Replica 1 has.

[sarbesh]

@vbabak won't this be a dependency issue if the Replica 1 fails to sync, Replica2 will also be out-of sync. I think it would be better to have each replica pull from master.