Django-hijack

* Added support for Django 1.11
* Reworked tox and travis setup

- Add French and Czech translations
- Include compiled messages in package

- Django 1.10 compatibility
- Drop support for Django 1.7 (might still work, but tests are allowed to fail)
- Add template filter `request|is_hijacked`
- Improve error handling in notification template tag

- Make hijacking via POST a default requirement
- Introduce a setting `HIJACK_ALLOW_GET_REQUESTS`
- Move Django admin integration to a separate package as it depends on GET (https://github.com/arteria/django-hijack-admin)
- **If you currently use the admin integration, follow the instructions there when upgrading**
- The setting `HIJACK_DISPLAY_ADMIN_BUTTON` is not used anymore.
- Pass request to signals
- Tests for custom decorators

- Fix end-of-hijack session cleanup code
- Don't save hijacked user at login; disconnect update_last_login instead
- Avoid encoding error in setup.py