Implement connection timeout

Is there a downside to implementing the connection timeout using the Future timeout feature?

I originally started out with [your suggestion to implement a first-class Celluloid::Timeout](https://groups.google.com/d/msg/celluloid-ruby/wNPmox7eowI/OorElxzYHHIJ). But my first cut at that used this same Future-based strategy: [gist](https://gist.github.com/simonrobson/5393451)