document how to change daemon ports

this more clearly explains that the daemon is listening on the network. it also hints as to how to change the listening ports. this is also related to #874

cmd/ipfs/daemon.go

@@ -38,7 +38,14 @@ over the network. Most applications that use IPFS will do so by
 communicating with a daemon over the HTTP API. While the daemon is
 running, calls to 'ipfs' commands will be sent over the network to
 the daemon.
-`,
+
+The daemon will start listening on ports on the network, which are
+documented in (and can be modified through) 'ipfs config Addresses'.
+For example, to change the 'Gateway' port:
+
+    ipfs config Addresses.Gateway /ip4/127.0.0.1/tcp/8082
+
+Make sure to restart the daemon after.`,
 	},
 
 	Options: []cmds.Option{