add django 3.0 to the ci

.travis.yml

@@ -9,6 +9,7 @@ python:
 
 env:
   - DJANGO_VERSION=django-22
+  - DJANGO_VERSION=django-30
 
 matrix:
   fast_finish: true

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 envlist =
-    {py36,py37,py38}-django-22
+    {py36,py37,py38}-django-{22,30}
 
 [testenv]
 setenv =
@@ -8,6 +8,8 @@ setenv =
 commands = pytest --cov=django_cryptolock tests/
 deps =
     -r {toxinidir}/requirements_test.txt
+    django-22: django>=2.2,<3.0
+    django-30: django>=3.0,<3.1
 basepython =
     py38: python3.8
     py37: python3.7