Adding a progressLabel option.

Greetings people of earth.  

I have a situation where I need to render progresses that exceed 100%.  Of course, I don't really want the bar to extend past the 100% mark so I set the progress value to 100%.  I really just want the label rendered over the bar to show the real percentage with the overage, so I set labelProgress to that value and all works as it should.

You may want to approach this problem a little differently and I respect that, but if quick and dirty hacks are to your liking, I humbly submit this pull request.

Peace be upon you.