python-3.7-3.8: Add Python 3.7 and 3.8 in Travis and update Django 2.2 to latest minor version.
python-3.7-3.8: Add Python 3.7 and 3.8 in Travis and update Django 2.2 to latest minor version.

Starou/django-thumborstorage,Starou/django-thumborstorage