Mostly repackaging, but usage remains the same except for `__version__`.
- `setup.py` now pins spacy version to `spacy<4.0.0,>=3.0.0` because it does not work with `spacy<3`
- dev-extras now include `spacy-transformers` to run the tests
- `__version__` variable removed from library files as it was causing import errors during a development install. If
you really need to get the version, there are [other ways](https://stackoverflow.com/a/32965521/1150683)