Optional jQuery

I made a small change to spritz.js, which detects if jQuery is loaded, and if not, uses `document.querySelector` instead. The output parameter can either be a selector string or a DOM element. If you are using jQuery, this change has no effect on the behavior.

I also added index-no-jquery.html, which is a non-jQuery port of the original index.html.

There are two reasons I thought this would be worthwhile. First off, it's always nice not to require jQuery when you don't have to. Secondly, this simplifies creating a bookmarklet, since it means the bookmarklet doesn't have to handle conflicts with existing jQuery on the page.