Django-tables2

- Do not perform extra `COUNT()` queries for non-paginated tables. Fixes [551](https://github.com/jieter/django-tables2/issues/551)

- Add new method `paginated_rows` to `Table` to replace fallback to non-paginated rows in templates.
- Prevent mutation of the template context `{% render_table %}` is called from (fixes [547](https://github.com/jieter/django-tables2/issues/547))
**Possible breaking change**: the context variables of the template `{% render_table %}` is called from is no longer available in the table's template. The `table` variable has an attribute `context`, which is the context of the calling template. Use `{{ table.context.variable }}` instead of `{{ variable }}`.

- Define and use `get_table_data` in `MultiTableMixin` [538](https://github.com/jieter/django-tables2/pull/538) by [vCra](https://github.com/vCra) (fixes [#528](https://github.com/jieter/django-tables2/issues/528))
- Added `{% export_url <format> %}` template tag.
- Allow passing a `TableData`-derived class to the data argument of the `Table` constructor, instead of a QuerySet or list of dicts.

- `BoundColumn.attrs` does not evaluate `current_value` as `bool` [536](https://github.com/jieter/django-tables2/pull/536) by [pachewise](https://github.com/pachewise) (fixes [#534](https://github.com/jieter/django-tables2/issues/534))
- Allow more flexible access to cell values (especially useful for django templates) (fixes [485](https://github.com/jieter/django-tables2/issues/485))

- Follow relations when detecting column type for fields in `Table.Meta.fields` (fixes [498](https://github.com/jieter/django-tables2/issues/498))
- Renamed `Table.Meta.template` to `template_name` (with deprecation warning for the former) [542](https://github.com/jieter/django-tables2/pull/524) (fixes [#520](https://github.com/jieter/django-tables2/issues/520))
- Added Czech translation [533](https://github.com/jieter/django-tables2/pull/533) by [OndraRehounek](https://github.com/OndraRehounek)
- Added `table_factory` [532](https://github.com/jieter/django-tables2/pull/532) by [ZuluPro](https://github.com/ZuluPro)

- Fix typo in setup.py for `extras_require`.