Rewrote jQuery.html to focus more on shim configuration (#675)

Hi!
Saw issue #675 about re-writing the documentation for jQuery + require.js to use the shim config instead.

This pull request changes jQuery.html to contain an example of how to use the shim config for dev and for building, and also shows a more advanced alternative where jQuery is excluded from the built product and loaded from a CDN.

I still think the require-jquery example make sense, and I've created an updated version of it here: https://github.com/karlwestin/require-jquery/tree/fix-jquery-documentation

I'd be happy to take feedback and change stuff :)