Slave removal: Make obvious in redis.conf what a replica is.

redis.conf

@@ -267,6 +267,11 @@ dir ./
 # Master-Replica replication. Use replicaof to make a Redis instance a copy of
 # another Redis server. A few things to understand ASAP about Redis replication.
 #
+#   +------------------+      +---------------+
+#   |      Master      | ---> |    Replica    |
+#   | (receive writes) |      |  (exact copy) |
+#   +------------------+      +---------------+
+#
 # 1) Redis replication is asynchronous, but you can configure a master to
 #    stop accepting writes if it appears to be not connected with at least
 #    a given number of replicas.