Add highlight.js support for markdown

[marcoscaceres]

When using markdown, it'd be nice to not have to wrap things in a <pre> tag to get highlight support. So you can just use back-ticks and specify the language.

[halindrome]

I am confused. I thought ReSpec used google-code-prettify.js. That's what is in the js directory in the tree.

[marcoscaceres]

Yes, you are correct - sorry about the confusion: the one was not on npm and was not as supported as hljs, so I swapped it. This one works the same, but allows for updates, etc.

[halindrome]

Sorry - what is "this one" in this context?

[marcoscaceres]

Highlight.js === this one.