Merge pull request #25 from uzumaxy/fix/travis

Updated python version for Travis CI

Author: eterey

.travis.yml

@@ -6,7 +6,8 @@ python:
   - "3.5"
   - "3.6"
   - "3.7"
-  - "3.8-dev"
+  - "3.8"
+  - "3.9-dev"
 
 install:
   - pip install codecov tox