Adds Stylus support to brunch.
Also includes nib cross-browser mixins.
Add "stylus-brunch": "x.y.z" to package.json of your brunch app.
Pick a plugin version that corresponds to your minor (y) brunch version.
If you want to use git version of plugin, add
"stylus-brunch": "git+ssh://git@github.com:brunch/stylus-brunch.git".