Include converter functionality to the packaged code

[pablo-de-andres]

In our data2rdf tool we use your converter.py file.

If this package was published on Pypi (#56), it would not be reachable given the current setup. Do you think it would make sense to include the converter in the code, so that it can be imported and used inside a Python script (without having to call it via the shell?)

If you agree and it would help you, we would be happy to make a PR with a possible implementation 🙂