fix malformed output since stack should begin with message

This should fix #4 so that the same error now looks like this:
![screen shot 2014-08-23 at 7 52 30 pm](https://cloud.githubusercontent.com/assets/1820410/4022214/a22d62b0-2b20-11e4-8b4d-07c62f6bb3c2.png)