Add documentation and link support for jQuery

This is a pull request for [Issue #37](https://github.com/marijnh/tern/issues/37) which I just raised.

It adds documentation notes and links for jQuery, using the `jQuery.json` file.  I've tested it in the demo and it works fine.  I'm happy to add tests if necessary, though I'm unsure of what I'd add since this is a data change only, no code changes involved.