Added error_queue parameter to update queues docs

![editing iron_mq_php readme md at master iron-io iron_mq_php 2014-06-24 16-08-55 2014-06-24 16-08-56](https://cloud.githubusercontent.com/assets/1712162/3379629/b37e3d56-fbf4-11e3-99ce-19b61dc4807c.png)