Update django-extensions to 1.7.9

[pyup-bot]

There's a new version of django-extensions available.
You are currently using 1.7.8. I have updated it to 1.7.9

These links might come in handy: PyPI | Changelog | Repo | Docs

Changelog

1.7.9

---

Changes:

• Fix: AutoSlugField, foreignkey relationships
• Fix: shell_plus, supported backends 'postgresql' for set_application_name
• Improvement: various commands, Add syntax highlighting when printing SQL
• Improvement: pipchecker, treat rc versions as unstable
• Improvement: shell_plus, allow to subclass and overwrite import_objects
• Improvement: shell_plus, fix SHELL_PLUS_PRE_IMPORTS example
• Improvement: setup.py, fix and unify running tests
• Improvement: runserver_plus, add RUNSERVERPLUS_POLLER_RELOADER_TYPE setting
• Improvement: generate_secret_key, use algoritme from django
• Docs: fix grammer and spelling mistakes

Got merge conflicts? Close this PR and delete the branch. I'll create a new PR for you.

Happy merging! 🤖

[mention-bot]

@pyup-bot, thanks for your PR! By analyzing the history of the files in this pull request, we identified @ad-m to be a potential reviewer.

[coveralls]

Coverage remained the same at 82.541% when pulling cbb81a2 on pyup-update-django-extensions-1.7.8-to-1.7.9 into 219a9ac on master.

[pyup-bot]

Closing this in favor of #112