Merge pull request #26 from yamijuan/master

fixed travis for older python versions vs newer django versions

.travis.yml

@@ -18,6 +18,21 @@ env:
   - DJANGO="django==1.9.13"
   - DJANGO="django==1.8.19"
 
+matrix:
+  exclude:
+   - python: "3.5"
+     env: DJANGO="django==3.1.3"
+   - python: "3.5"
+     env: DJANGO="django==3.0.11"
+   - python: "3.4"
+     env: DJANGO="django==3.1.3"
+   - python: "3.4"
+     env: DJANGO="django==3.0.11"
+   - python: "3.4"
+     env: DJANGO="django==2.2.17"
+   - python: "3.4"
+     env: DJANGO="django==2.1.15"
+
 install:
   - pip install $DJANGO
   - pip install coveralls