Error event includes original error

It would be nice for reporters to have access to the original error in case they want to do something with it.

In my case, I am writing a reporter for Rollbar, and their library requires the error object in order to do their own parsing.
Please check the documentation for `Code.expect` [here](https://github.com/hapijs/code#table-of-contents). Some of your assertions are no longer correct.