Adding spec for capturing remote DOI error

In the event that you are attempting to mint a DOI
And you receive some remote service exception (i.e. invalid data)
Transform the exception into something meaningful

And more importantly make sure to use :data instead of :payload
as :payload is not defined within that context.
Merge pull request #1 from jeremyf/adding-spec-for-doi-remote-error

Adding spec for capturing remote DOI error