[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.
> The non-CSS stylus syntax goes against the webdev CSS style-guide. See http://mozweb.readthedocs.org/en/latest/css-style.html

OK you have the final point! :)