Add support for Fluidity CSS

Hey there. I know you don't know me from Adam, but I've written a small stylus library called fluidity that I would like to have supported in connect-assets. I've recently published the lib to npm and forked connect-assets in order to add support. It's implemented in an identical manner as 'nib' so it shouldn't be to big a deal. I'm currently just using my fork of connect-assets without any trouble, but if it could be in the base repo that would totally make my day. Thanks for your time and all your excellent work and if you can just let me know what you think?

You can check out fluidity at fluiditycss.com (Still being put together I hope to have my ducks in a row for a public release in the next week or so)