Update django-extensions to 2.1.3

[pyup-bot]

This PR updates django-extensions from 2.0.7 to 2.1.3.

Changelog

### 2.1.3 ``` ----- Changes: - Fix: Readme, add direct linkt to screencast video - Fix: graph_models, regression under Python 2 - Fix: ForeignKeyAutocompleteAdmin, 2.0.8 breaks ForeignKeyAutocompleteAdmin - Fix: AutoSlugField, fix regression when copying an autoslug model require the explicit clearing of the slug if it needs to be recalculated - Fix: technical_response, check for AttributeError - Improvement: graph_models, Add feature disable_abstract_fields - Improvement: AutoSlugField, Add overwrite_on_add - Improvement: runscript, Improve module existence test in runscript ``` ### 2.1.2 ``` ----- Changes: - Fix: AutoSlugField, fix check on list or tuple type ``` ### 2.1.1 ``` ----- ``` ### 2.1.0 ``` ----- Changes: - Fix: travis ``` ### 2.0.9 ``` ----- Changes: - Improvement: use README as project description on PyPI ``` ### 2.0.8 ``` ----- Please stop using ForeignKeyAutocompleteAdmin edition :-) Changes: - Fix: special markers in runserver_plus.rst - Fix: shell_plus, refactor reading pythonrc file outside of exec(compile(...)) - Fix: reset_db, fix default utf8 support - Fix: autoslugfield, Fix autoslug generation when existing model is copied - Improvement: Cleanup management commands options after argparse migration 916 - Improvement: sqldiff, add more tests - Improvement: sqldiff, add DurationField and SearchVectorField - Improvement: shell_plus, add more tests - Improvement: shell_plus, backport macos fix for tab completion - Improvement: clear_cache, add --all option - Improvement: pipchecker, treat dev versions as unstable - Deprecation: ForeignKeyAutocompleteAdmin, Django 2.0 has similar capabilities, which are much better supported. ```

Links

- PyPI: https://pypi.org/project/django-extensions - Changelog: https://pyup.io/changelogs/django-extensions/ - Repo: http://github.com/django-extensions/django-extensions