Restrict CI to Python 3.6+

setup.py to be fixed if compat below 3.6 isnt needed.

Author: jayvdb

.travis.yml

@@ -1,8 +1,7 @@
 language: python
 python:
-  - 2.7
-  - 3.4
   - 3.6
+  - 3.7
   - 3.8
 install: pip install tox-travis
 script: tox