Add canonical repr of Versa model for use in tests

I opted for JSON instead of pprint as it seems pprint hasn't yet figured out how to reasonably represent OrderedDicts, and because I just solved the JSON problem elsewhere ;) AFAICT, we shouldn't be serializing any non-JSON-serializable types in Versa

http://bugs.python.org/issue7434

Also fixed what appeared to be a typo on line 142.