User role change email notification

Dear armember team,

The "armember" user role is added or removed depending on plan already, so there is some kind of user role manipulation already inside the armember code. It would be nice to have an email sent to the user whenever the admin changes his role. This would be useful in cases where the user is registered in wordpress as a "Subscriber" but hasn't still been assigned the armember role by a plan. So if the admin wants to have further cotrol over that for example by another plugin that checks user roles, it would be nice to have an email notification when the user role changes to "Author" for example.

This would also be useful to be added to the member's profile as an entry. Right now the only way for the user to see his role is by assigning a badge to his profile page.

Vassilis