fix many version errors

Pipfile

README.md

constance/admin.py

constance/backends/database/__init__.py

constance/backends/database/models.py

constance/checks.py

constance/signals.py

opds_catalog/feeds.py

opds_catalog/models.py

opds_catalog/opdsdb.py

opds_catalog/urls.py

requirements.txt

sopds/settings.py

sopds/urls.py

sopds_web_backend/urls.py

sopds_web_backend/views.py