Update index.html

First of all, I love the idea of relative protocol.

In the Readme.md file you have stated "The latest jQuery via CDN, with a local fall back.". Instead of manually updating the version every time we can use the latest version of library via jQuery's CDN. But there are few issues:
1. jQuery's CDN might not be as reliable as Google's CDN.
2. Either way when falling back to local we have to manually update the library version 
3. Developers must make sure that if their site is not always offline then the latest jquery version must not brake their script