Update django-extensions to 1.8.1

[pyup-bot]

There's a new version of django-extensions available.
You are currently using 1.7.9. I have updated it to 1.8.1

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

Changelog

1.8.1

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Changes:

• Build: use tox's 'TOXENV' environment variable
• Fix: resetdb, fix problem that 'utf8_support' option is ignored
• Improvement: export_emails, moved custom csv UnicodeWriter (for py2) into compat.py
• Translations: pt, removed since it was causing issues with the builds
  if anybody wants to update and fix it that would be
  much appreciated !

1.8.0

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UUIDField has been removed after being deprecated.

Deprecation schedule for JSONField has been removed after requests from the
community.

Changes:

• Fix: runserver_plus, fixed Python 3 print syntax
• Fix: sqldiff, Use 'display_size', not 'precision' to identify MySQL bool field
• Fix: export_emails, fix and refactor the command and all its output options
• Improvement: tests, added Python 3.6 and PyPy3.5-5.8.0
• Improvement: clear_cache, add --cache option to support multiple caches
• Improvement: runserver_plus, limit printing SQL queries to avoid flooding the terminal
• Improvement: shell_plus, limit printing SQL queries to avoid flooding the terminal
• Docs: graph_models, document including/excluding specific models
• Docs: shell_plus, added PTPython

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

Happy merging! 🤖