I would definitely emphasize that it's pure CSS, because it wasn't obvious to me when I looked. Instead of

    custom css progress bars with minimal effort!

you could write:

    Pure CSS progress bars with minimal effort!

(Yeah, the lack of capitalization looks a bit shoddy to me.)

Aside from that, it looks great. That said, I think a JavaScript helper to complement it would be great; I am using NProgress in several apps, and I like the fact that I can just start and stop it, and it will just do its thing.