added srcAbs to the options passed to the middleware.
it defaults to false and removes /css from the path if true.
this enabled my to load styl files from
/views/themename/style.css
and compile them to
/public/css/style.css

i am not too sure if you want to merge this into stylus the way it is,
but i couldnt find a nicer way to implement this right now and figured,
since the tests are still working i could as well just pull request instead of opening an issue.