Add a hint about people not in your contact list

If you invite a person to a bubble that is not yet a Rainbow user, the person may join Rainbow and then be available in the bubble, and you can even chat with them, but you never see a presence indicator until that person has been added to your contact list.

It would be helpful to have a hint (mouseover maybe) to inform you that a person has not been added to your contact list. And to take this even further, an action that allows you to immediately add said person to your contact list without having to send another invite.