Conform Travis CI testing to Python versions supported in setuptools

setuptools in setup.py reports Python 2.7 and Python 3.4-3.7 (inclusive) support.

Conform the python version testing in Travis CI to match each of these versions,
as good practice to avoid future conflicts or regressions.

Author: Echelon9

.travis.yml

@@ -2,6 +2,7 @@ language: python
 # Existing Python versions
 python:
   - "2.7"
+  - "3.4"
   - "3.5"
   - "3.6"
 # Enable 3.7 without globally enabling sudo and dist: xenial for other build jobs