Implement state machine

[mstade]

Webmachine is a pretty cool take on HTTP processing, and I reckon a nappy version of the state machine could likely be implemented as a separate library. This would be very cool, because HTTP is pretty ubiquitous and it'd provide the node community with a much needed sane and grown up alternative to the oh-so-sad express. I don't care much for the way Webmachine works in general (it's ReqData API is weird and Context is a convenient hack around the how-do-I-pass-a-bunch-of-state-around? problem) but the idea that HTTP processing is a state machine with sane defaults and pluggable processors would be pretty nifty. Coupled with persistent data structures for messages, it could also allow for some seriously cool debugging opportunities, like a visual debugger much like what Webmachine provides.