#16 Add abbreviation description for AGPLv3+

I personally don't really find this to be a good idea. One of the points of markdown is that it's also easily readable in a text editor. This HTML makes that a bit worse, for negligible benefits (if someone doesn't know what AGPL is, having a long version on mouse-over isn't going to help them understand). If anything would change here, I'd rather it just be adding a sentence like "Check LICENSE for more information". Thanks though.