About a year or 2 ago I saw someone here on HN suggest doing this very thing. If my memory is correct, I think it was after jQuery's CDN once became compromised.
http://jimkeener.com/posts/http is my concept from 2013 (hash attribute) and I'm sure I'm not the first, either. It's an old idea and I'm _very_ glad to see someone doing it!
EDIT: I just reread my post and there are some wonky ideas mixed in with (what I think are) decent ones. Sorry!
[Edit] I think this was the discussion, just over a year ago! - https://news.ycombinator.com/item?id=8359223