[WIP] Bug 1036486 less2stylus

See https://bugzilla.mozilla.org/show_bug.cgi?id=1035783

[staticfiles](https://github.com/mozilla/olympia/pull/110) PR needs to be landed before.
> Again, that's a valid argument, and I'm not arguing against that. But at this point, why Stylus? Why not vanilla CSS? I would be the first to sign for this move.

We're not talking about that or node deps or any other things - we're talking about whether changing to  a non-standard stylus syntax (within mozilla projects) is a good thing or not.

The non-CSS stylus syntax goes against the webdev CSS style-guide. See http://mozweb.readthedocs.org/en/latest/css-style.html 

> Use Stylus but write it like plain CSS

We should have really compelling reasons for going against that.