This fixes a regression introduced in the last
feature merge.
The RestfulExceptionHandler will now fall-back to using the HTTP status
message for an API exception that has a code but no defined slug. This
of course can be overridden simply by setting a slug, just as before.
Easier to read..
Merge pull request #7 from Rican7/bugfix/restful-exception-handler-slug

Bugfix - REST exception handler slug regression