Added server command to ./bin/ember

I'm using pushState with my Ember app, and came in handy to just have a basic server available in order to serve clean URLs, so I've added a rudimentary implementation. Not sure if this is something that people would find useful, but thought I'd throw it into the mix and have a discussion.

Testing wise, not sure what would be beneficial, I was going to just have an initial test to see whether it started successfully, but having issues detecting a "listening" event once connect has created the connection. If anyone wants to take a look and make suggestions, I'd be grateful.

Feedback?