Update hightlight.js, beautify.js, and add line numbering, plus CUDA syntax options

Fixes Issue https://github.com/tsenart/sight/issues/53
`id` and `class` were redundant so I removed the `class="line-numbers"`. This is actually the container for all the number `span`s not the numbers themselves. `cl` stands for "clear", I changed this to `clearfix` to be more verbose.