CSS guidelines

[javigomez]

Just found a tweet about this:
http://cssguidelin.es/

Adding it here to review it when we do the Code Style code sprint.

[photodude]

I think this is partially addressed with PR #155 which adds SCSS standards to the manual
@mbabker thoughts?

[mbabker]

I'm pushing to have a full CS team set up that would address styling for all languages. Let's leave it until they get running and have a chance to review.