Sentinel example config: warn about protected mode.

sentinel.conf

@@ -1,5 +1,21 @@
 # Example sentinel.conf
 
+# *** IMPORTANT ***
+#
+# By default Sentinel will not be reachable from interfaces different than
+# localhost, either use the 'bind' directive to bind to a list of network
+# interfaces, or disable protected mode with "protected-mode no" by
+# adding it to this configuration file.
+#
+# Before doing that MAKE SURE the instance is protected from the outside
+# world via firewalling or other means.
+#
+# For example you may use one of the following:
+#
+# bind 127.0.0.1 192.168.1.1
+#
+# protected-mode no
+
 # port <sentinel-port>
 # The port that this sentinel instance will run on
 port 26379
@@ -178,4 +194,3 @@ sentinel failover-timeout mymaster 180000
 #
 # sentinel client-reconfig-script mymaster /var/redis/reconfig.sh
 
-