Autocomplete select another contact on Membership Signup form should put up notification is this is a renewal (i.e. if the selected contact has an existing membership)

Per our IRC discussion ... when user selects a contact from autocomplete box in online contribution membership signup form, if the selected contact already has a membership, a notification should be given as we do for logged in user and for cid=NNN situations (see screenshot). The notification can be a pop-up style rather than injecting the green div with message if that's easier, but it should include the existing membership type and expiration (same text as green box).