New Syntax Highlighting

Right in time for @bschwartz's birthday, new syntax highlighting in the doc!

This is based on the `codeblock` Jekyll plugin @freerobby uses for his blog. 

New syntax:

    {% codeblock ruby_example.rb %}
    ...ruby!...
    {% endcodeblock %}

This update also includes updated styling for inline code blocks (use backticks) and full width code spans (use class `full_width`).

Yeah buddy! :+1: