Depend on publicly shipped version of Narya.
Added SBT build. I can't work with stone tools in my old age.
Added code for writing a simple miso scene model to JSON.

Wow, writing to JSON is way simpler than writing to HTML. Too bad JSON wasn't
around and popular twelve years ago.
Allow parsing from InputStream.
Added a little test of the JSON writer.

I'm also using this test to do the conversions I need, since I just need our
two test scenes in JSON format.