Merge pull request #28 from ccnmtl/nikolas-patch-3

Test on django 2.1

Author: sdreher

.travis.yml

@@ -7,10 +7,13 @@ env:
 - DJANGO="Django>=1.8.0,<1.9.0"
 - DJANGO="Django>=1.11,<1.12.0"
 - DJANGO="Django>=2.0,<2.1"
+- DJANGO="Django>=2.1,<2.2"
 matrix:
   exclude:
   - python: '2.7'
     env: DJANGO="Django>=2.0,<2.1"
+  - python: '2.7'
+    env: DJANGO="Django>=2.1,<2.2"
 install:
 - pip install $DJANGO
 - pip install flake8