Log Message:
Update to 0.5.0

Upstream changes:
Version 0.5.0, 6th March 2020:
Drop support for Python 2.

Compatiblity fix for Django 2.2 and Django 3.0.

Version 0.4.6, 14th October 2017:
Fix IntegrityError while saving inconsistent tags

Update tag name length to use MAX_TAG_LENGTH setting

Version 0.4.5, 6th September 2016:
Fix on the previous compatiblity fix.

Version 0.4.4, 5th September 2016:
Compatiblity fix for Django 1.10