Use Jekyll's native templating and rendering

Sorry. This is the same as my previous pull request, just rebased and on a different branch.

--------

Instead of using printf in a build script, you can use GitHub Pages' built in system — Jekyll. All you have to do now is edit `README.md` (which is a symlink to `_includes/HTML6.md`) and let Jekyll handle the rest!

I also removed the jQuery library after changing jQuery.ready (`$()`) to `window.onload`.