Clade Ontology in Python (Jan 2019)

We initially built the Clade Ontology with a Python-based library to convert Phyloreference Exchange (PHYX) files into OWL. We later replaced this with a Node.js-based library. This tag records the Python-based library as it was when we replaced it. While we do not currently intend to further work on this library, it is made available here for reuse under the MIT license. A test report from this tag is available on Travis CI.