Custom themes

[rstacruz]

I'd like to make custom themes for DocumentUp.

Can we have an option to, say, pass it via http://documentup.com/kriskowal/q?css=http://... ?

[jeromegn]

Ok, for now, I welcome a PR :) for a new theme.

Did you want to add flatdocs in here?

If you add it to app/assets/stylesheets/themes/[your theme].css.scss, I will gladly announce it and show it off in the readme!