CSS Updates and Highlight.js

Made several CSS style updates to make the preview look (I think) a little nicer. Primarily just inherit fonts from oC's default CSS, clean up some of the headings, restore numbering to ordered lists (fixes issue #5), and clean up list styles.

Additionally, I've introduced highlight.js support for code blocks and it's default syntax highlighting stylesheet.

I have adjusted the top padding of the preview pane -- I only have an oC 7 installation available, but the updated spacing prevents the preview's scrollbar from appearing under the oC navigation bar.

Tested with IE 11 and Firefox 31 in Windows, and Firefox (Iceweasel) 31 in Linux.