Send should return the socket to request responder apis

When the websocket transport was changed from socket.io to engine.io, the API for request responders was inadvertently changed.  I think this was due to the change in language and the fact that coffeescript always returns the final value.   

I was using this returned value in ss-angular, and I think it's a good thing to do, so I have fixed it with this very simple change.  The related bug in ss-angular is here:

https://github.com/polidore/ss-angular/issues/16

Merging this in and releasing to NPM would be great for ss-angular users out there. 

Thanks!