Add callback to client's disconnect method

In my node to node client i currently have something like this:

``` 
process.on('SIGINT', function() {
  console.log('Got SIGINT signal, let me just disconnect...');
  client.disconnect();
  setTimeout(function() {
  	process.exit(0);
  }, 1000);
  
});
``` 

I believe this approach is somewhat cleaner:
``` 
process.on('SIGINT', function() {
  console.log('Got SIGINT signal, let me just disconnect...');
  client.disconnect(function() {
  	process.exit(0);
  });
});
``` 

However - i dont know if this will break the api ? - the client.disconnect() should work just as before if no callback is provided