Control channel from strong-cluster-control

@kraman, can you review?

Implementation might need adjustment once I use it in strong-supervisor, but this is basically what I needed from strong-cluster-control.
So, observing the code, sockets are initialized immediately, but not marked as writeable, so I believe writing to a stream is fine, it buffers, and data will flow.

I tested with this:
```
var net = require('net')
s=net.connect(80, 'example.com')
s.write('some thing\n\n')
s.on('data', function(data){
  console.log('data: %s', data);
});
```

The HTTP server at example.com gets the network write, despite that the .write() occurs before connection complete.