Get rid of sanitize dependency in docs

[zpao]

If OSX didn't ship with Ruby 1.8.7, this wouldn't be a big deal, but it does and I would rather not make everybody jump through hoops to be able to contribute to documentation (and see what they're contributing).

Right now, even when using 1.8, sanitize has a nokogiri dependency that requires Ruby 1.9.2. I think there's probably something that could be done in those projects to fix this so feel free to take that path.

This dependency was introduced with #360.

[vjeux]

👍

[sophiebits]

Mavericks comes with 2.0.0p247 now.