Fix bug 862003 - Implement Prism Highlighter

https://bugzilla.mozilla.org/show_bug.cgi?id=862003

So with this we have a decision, and that decision is to keep our current highlighter which looks OK in IE8, or move to something that's faster and more extensible but sacrifice line numbering and some cod formatting in IE8.

The IE8 formatting issue with Prism is that line-breaks aren't always properly displayed; i.e. two "LI" elements may be displayed on the same line.

So...it's up to the team as to how we want to display this.  If our IE8 audience is small, I think we should use this.