Merge pull request #20 from evrardjp/fix_ci

Update python runtime environments

Author: richmahn

.travis.yml

@@ -1,9 +1,8 @@
 language: python
 python:
-- '2.7'
-- '3.3'
-- '3.4'
 - '3.5'
+- '3.6'
+- '3.7'
 install:
 - pip install -r requirements.txt
 - pip install -r test_requirements.txt