Add note about aptly serve to command output

cmd_publish.go

@@ -99,6 +99,7 @@ func aptlyPublishSnapshot(cmd *commander.Command, args []string) error {
 	fmt.Printf("Now you can add following line to apt sources:\n")
 	fmt.Printf("  deb http://your-server/%s %s %s\n", prefix, distribution, component)
 	fmt.Printf("Don't forget to add your GPG key to apt with apt-key.\n")
+	fmt.Printf("\nYou can also use `aptly serve` to publish your repositories over HTTP quickly.\n")
 
 	return err
 }