Update django-tables2 to 1.18.0

[pyup-bot]

There's a new version of django-tables2 available.
You are currently using 1.16.0. I have updated it to 1.18.0

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

Changelog

1.18.0

• Follow relations when detecting column type for fields in Table.Meta.fields (fixes 498)
• Renamed Table.Meta.template to template_name (with deprecation warning for the former) 542 (fixes 520)
• Added Czech translation 533 by OndraRehounek
• Added table_factory 532 by ZuluPro

1.17.1

• Fix typo in setup.py for extras_require.

1.17.0

• Dropped support for Django 1.8, 1.9 and 1.10.
• Add extra_context argument to TemplateColumn 509 by ad-m
• Remove unnecessary cast of record to str 514, fixes 511
• Use django.test.TestCase for all tests, and remove dependency on pytest and reorganized some tests 515
• Remove traces of django-haystack tests from the tests, there were no actual tests.

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

Happy merging! 🤖

[pyup-bot]

Closing this in favor of #388