Add usage messsage on no permission

src/de/steamwar/bungeecore/commands/JoinmeCommand.java

@@ -41,7 +41,10 @@ public class JoinmeCommand extends SWCommand {
 
     @Register(description = "JOINME_USAGE")
     public void genericCommand(ProxiedPlayer player) {
-        if (!player.hasPermission("bungeecore.joinme")) return;
+        if (!player.hasPermission("bungeecore.joinme")) {
+            Message.send("JOINME_USAGE", player);
+            return;
+        }
         Message.broadcast("JOINME_BROADCAST", "JOINME_BROADCAST_HOVER",
                 new ClickEvent(ClickEvent.Action.RUN_COMMAND, "/join " + player.getName()), player.getName(), player.getServer().getInfo().getName());
     }