More sophisticated AnnotatedException pretty-printing

[chris-martin]

There is currently some logic for pretty-printing AnnotatedExceptions (the underlying exception, a call stack if present, and any other annotations) in the displayException implementation for AnnotatedException and in the Freckle.App.Test.Hspec.AnnotatedException module.

1. This should be improved with a pretty-printing library
2. This should be upstreamed from freckle-app at least to freckle-exception, if not all the way out to annotated-exception (receptive to PR).