Switch Apertium APy to use pipenv from pip
Apertium APy has lots of development dependencies and some real ones but the transitive dependencies are all also enumerated, making it difficult to see what's going on. It would be good to use pipenv so that these real development dependencies are clearly separated from transitive dependencies. Please submit a pull request that transitions this repository from the
requirements.txt model to the
Pipfile[.lock] model and updates the README as appropriate.