Revert "Disabled Kramdown support temporarily due to Github Pages issues."

This reverts commit f0c94c38fa5ea444d54c6aa64319667ad0971f51.
Added Rakefile to exclude list.
Set destination back to default.
Removed old content from sitemap.
Updated sidebar footer content.
Added red hover color to all links.
Added plugin to rename footnote links on index page. Courtesy of http://syeong.jcsg.com/2012/07/07/octopress-footnote-problem/
Added jekyll-s3 deploy support.