Install Falcon, IPython, Gunicorn and HTTPie

- Falcon is a lightweight Python web framework
- IPython is a more powerful REPL
- Gunicorn is a WSGI (Python's equivalent of Rack) server
- HTTPie is a pretty cURL replacement
Add a simple app

- checks that the client accepts JSON
- returns hardcoded data for GET on index
- returns data parsed from request on PUT for a court by UUID
Validate against a simple JSON schema for PUT request

- return 422 if validation against the schema fails
- return 500 if the schema is invalid

This also defines a custom exception for the 422 status code; this
status doesn't have an error class already in Falcon (perhaps because
it's defined in a different RFC?).
Document local setup and current behaviour in the README