Update django-tables2 to 1.17.0

[pyup-bot]

There's a new version of django-tables2 available.
You are currently using 1.14.2. I have updated it to 1.17.0

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

Changelog

1.16.0

This is the last version supporting Django 1.8, 1.9 and 1.10. Django 1.8 is only supported until april 2018, so consider upgrading to Django 1.11!

• Added tf dictionary to Column.attrs with default values for the footer, so footers now have class attribute by default 501 by mpasternak

1.15.0

• Added as=varname keyword argument to the {% querystring %} template tag,
  fixes 481
• Updated the tutorial to reflect current state of Django a bit better.
• Used OrderedDict rather than dict as the parent for utils.AttributeDict to make the rendered html more consistant accross python versions.
• Allow reading column attrs from a column's attribute, allowing easier reuse of custom column attributes (fixes 241)
• value and record are optionally passed to the column attrs callables for data rows. 503, fixes 500

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 #7141