Support Django 2.2 and 3.0

tox.ini

@@ -9,6 +9,13 @@ envlist=
     py36-django20,
     py35-django21,
     py36-django21,
+    py37-django21,
+    py36-django22,
+    py37-django22,
+    py38-django22,
+    py36-django30,
+    py37-django30,
+    py38-django30,
 
 [flake8]
 max-line-length=100
@@ -118,6 +125,47 @@ deps =
     Django>=2.1,<2.2
     {[base]deps}
 
+[testenv:py37-django21]
+basepython=python3.7
+deps =
+    Django>=2.1,<2.2
+    {[base]deps}
+
+[testenv:py36-django22]
+basepython=python3.6
+deps =
+    Django>=2.2,<3.0
+    {[base]deps}
+
+[testenv:py37-django22]
+basepython=python3.7
+deps =
+    Django>=2.2,<3.0
+    {[base]deps}
+
+[testenv:py38-django22]
+basepython=python3.8
+deps =
+    Django>=2.2,<3.0
+    {[base]deps}
+
+[testenv:py36-django30]
+basepython=python3.6
+deps =
+    Django>=3.0,<3.1
+    {[base]deps}
+
+[testenv:py37-django30]
+basepython=python3.7
+deps =
+    Django>=3.0,<3.1
+    {[base]deps}
+
+[testenv:py38-django30]
+basepython=python3.8
+deps =
+    Django>=3.0,<3.1
+    {[base]deps}
 
 
 [testenv:flake8]