Add documentation about rescue_responses in Configuring

Thanks! I also realized that the format isn't great. I'll send another pull request to fix both English and the style.

![screen shot 2014-09-27 at 10 00 04 am](https://cloud.githubusercontent.com/assets/386234/4430917/9d53071a-464e-11e4-8f4a-287960c36d63.png)