Hold the boat

This one is painful. I did not write good enough tests, and so the shutdown behavior I thought was working did not. There is somewhat of a race condition here where if the worker were writing to gearman we would wait, but ultimately this is just a big fail on my part:

![image](https://cloud.githubusercontent.com/assets/603357/4228195/688703b0-3956-11e4-9078-800647a45f76.png)

![screenshot 2014-09-10 18 53 37](https://cloud.githubusercontent.com/assets/603357/4228202/81a764a2-3956-11e4-9eaf-be8b22557ccb.png)


this should be an instance of `Error`, not just a string