Log Message:
py-django-filter: updated to 2.1.0

Version 2.1:

* Fixed a regression in FilterView introduced in 2.0. An empty QuerySet was
  incorrectly used whenever the FilterSet was unbound (i.e. when there were
  no GET parameters).  The correct, pre-2.0 behaviour is now restored.

  A workaround was to set strict=False on the FilterSet. This is no
  longer necessary, so you may restore strict behaviour as desired.

* Added IsoDateTimeFromToRangeFilter. Allows From-To filtering using
  ISO-8601 formatted dates.