v0.6.0

• Feature: Add LimitingServer to limit and keep track of open connections
  (#86 by @clue)

  $server = new Server(0, $loop);
  $server = new LimitingServer($server, 100);
  
  $server->on('connection', function (ConnectionInterface $connection) {
      $connection->write('hello there!' . PHP_EOL);
      …
  });

• Feature / BC break: Add pause() and resume() methods to limit active
  connections
  (#84 by @clue)

  $server = new Server(0, $loop);
  $server->pause();
  
  $loop->addTimer(1.0, function() use ($server) {
      $server->resume();
  });