Implement a number indicator.

[pamobo0609]

This is a great library which works perfectly and even though there's some other similar libs to this one, this is the best one I've used since the Jack Wharton one.
I don't know if it's too much or too early to ask for this, but I think a number indicator would be a great addition to this library.
I haven't found such a feature in another library as of yet.