Re-export lifted Test.Hspec expectations

Addresses https://github.com/hspec/hspec-wai/issues/22
As far as I know, the [Scotty](https://github.com/scotty-web/scotty) routing library catches errors and returns HTTP 500 responses, so anything using Scotty (and the library itself) may find it useful to know if an error is thrown during a WAI action. So there's at least one use-case off the top of my head. :wink: