Big thanks to Dmitry Groshev [1] for help getting PropEr tests into
Jiffy. These generate valid EJSON to check parsing as well as check
that random inputs don't cause segfaults or other nasty effects.
Future improvements would be to write a JSON generator as well as a
version that introduces known errors into the binary for checking known
parsing errors as well.
[1] https://github.com/si14Fixes: #10