Using python 3.7 too as well as testing multiple pylint versions

Author: Carl Crowder

.travis.yml

@@ -1,14 +1,17 @@
+dist: xenial
 language: python
 python:
   - "3.4"
   - "3.5"
   - "3.6"
+  - "3.7"
 env:
   - PYLINT=1.9.2
   - PYLINT=1.9.3
   - PYLINT=2.0.0
   - PYLINT=2.1.1
   - PYLINT=2.2.2
+  - PYLINT=2.3.0
   - PYLINT=master
 install:
   - |