2.3.0

• Handle making a column NOT NULL with a Django default value as backward incompatible.
  This should have been the case from the beginning, but it was not.
  When one uses the django-add-default-value lib, the operation should still be compatible.
• Improve behaviour of the --include-migrations-from option.
  When the given filename is missplelled, fail instead of linting all migrations.
  When the file is empty, lint no migrations instead of linting all migrations.
• Update libraries used for testing (tox, flake8, etc.)