py-cybox: updated to 2.1.0.16

Version 2.1.0.16
- Re-packaged 2.1.0.15 with newer setuptools to fix broken wheel.

Version 2.1.0.15
- Fully support PDFFile object.
- Add URI property to Artifact object.
- Support Object 'description' field.
- Add UnixUserAccount object.
- Fix error when PropertyTypes have 'delimiter' but no value.
- Allow setting 'condition' on Artifact object's RawArtifact propety.
- Support adding SSDEEP hashes.
- Don't include properties when adding Related Objects with inline=False.
- Handle 'event' property of Observables correctly.

(adam)