Log the error message, not the error class

This actually provides useful error messages. Previously you'd see
"TypeError" on the console. This is not useful. Now you'll see "fooBar()
is not a method". This lets you track down exceptions.

@stefanpenner: This is an iteration from our work yesterday. We need to log the error message and simply rethow the error itself. It seems the errors do not have a meaningful `toString()` method.