Use major releases for current package.json.

* This entails more checking to see if site compatibility busts e.g. if GH changes their OAuth then our site breaks with logins. Conversely our site won't break entirely if the package is updated beyond compatibility. Seems like an even tradeoff to me but we'll give it a try.
* Change README.md to match
* Clean up the headers a bit in README.md

Closes to #321

May affect a portion of #315
Add a missing CDN to README.md