Asciidoctor-skins

[tajmone]

I've come across @darshandsoni's asciidoctor-skins, a collection of alternative stylesheets for the native Asciidoctor backend.

The styles are nice, and MIT licensed. Unfortunately there aren't any Sass sources, but we could easily port a stylesheet to SCSS if we find one that we'd like to use.

This is approach is preferable to having to tweak the asciidoctor-stylesheet-factory, which relies on an old version of Foundation and on Compass (which has reached EOF).

At this point, anything that could speed up work is welcome.