Django-updown

- Add support for Django 2.0 (thanks to [agusmakmun](https://github.com/agusmakmun))

- Replaced IPAddressField in migration (thanks to [baster33](https://github.com/baster33))

- Fixed IPAddressField error (thanks to [agusmakmun](https://github.com/agusmakmun))

- Dropped support for Python 2.6
- Added Python 3 support
- Dropped support for Django < 1.8
- Django 1.8 & Django 1.9 are now supported
- Tests are run using tox (for all Python and Django versions)
- Switched to more semantic versioning
- Removed old south migrations, added Django migrations
- Refactoring and cleanup

- Fixed DateTimeField RuntimeWarning (thanks to [yurtaev](https://github.com/yurtaev))
- Tests are using Django 1.4.10 now

- Usage of `AUTH_USER_MODEL` instead of `auth.models.User` (thanks to [timbutler](https://github.com/timbutler))