Make best_match() return similar to parse_ctype().
Add tests on TypeRule.
Tune a docstring.
Fix up the name for an AVersion method.
Add tests for the Result class.
Pull out static methods

There's no reason that _parse_type_rule() or _uri_normalize() need
to be static methods, so pull them out and make them functions.
Add logging for _parse_type_rule().
Add content type to log message about token value.
Ignore unrecognized token values.
Add tests on _parse_type_rule().