message: Fixed example in sub.php
  The previous example is broken since v4.4.0
diff: <?php
  go(function () {
  -
  -
  $redis = new Swoole\Coroutine\Redis();
  $redis->connect('127.0.0.1', 6379);
  -//while (true)
  -{
  $msg = $redis->subscribe(array("msg_1"));
  + while ($msg = $redis->recv())
  + {
  var_dump($msg);
  }
  +});
  +go(function () {
  + $redis = new Swoole\Coroutine\Redis();
  + $redis->connect('127.0.0.1', 6379);
  + $msg = $redis->subscribe(array("msg_2"));
  + while ($msg = $redis->recv())
  + {
  + var_dump($msg);
  + }
  });
  