CLean up documentation for syntax highlighters

It was a bit all over the place, so I'm trying to organize it better.
Use stringex for URL escaping

Turns out stringex's to_url creates exactly the look I wanted to see. No
sense maintaining my own URL escaping function, then.
Add bundler setup to lib

I think I was supposed to do this way earlier, but I'm not familiar with
the bundler workflow yet. Oops.
Clean up quoting style

My use of single vs double quote was a bit haphazard so I cleaned it up.
I'm using single quotes by default.
Add basic Rakefile

The Rakefile's main task is to create new articles (with pre-baked front
matter). More tasks will probably be added in the future.