Use the latest compatible Django for each python unless specified otherwise

Author: Kevin Michel

tox.ini

@@ -21,9 +21,9 @@ deps =
     Flask-SQLAlchemy
     future
     # the sdk doesn't support earlier version of django
-    django1: django >= 1.10, <2.0
-    django2: django >= 2.2, <2.3
-    !django1-!django2: django >= 3.0, <4.0
+    py{27,34}-!django2-!django3,django1: django >= 1.10, <2.0
+    py{35}-!django1-!django3,django2: django >= 2.2, <2.3
+    py{36,37,38}-!django1-!django2,django3: django >= 3.0, <4.0
     django-fake-model
     pynamodb >= 3.3.1
     psycopg2