Trying to get travis to build on both 3.6 and 3.7

Author: Mohan Kishore

.travis.yml

@@ -1,8 +1,7 @@
 language: python
-python:
-- 3.6
 matrix:
   include:
+    - python: 3.6
     - python: 3.7
       dist: xenial
       sudo: true