update travis setup for linting

Author: RonnyPfannschmidt

.travis.yml

@@ -11,10 +11,10 @@ env:
 
 matrix:
   include:
-    - python: '2.7'
-      env: TOXENV=flake8
     - python: '3.5'
       env: TOXENV=flake8
+    - python: '3.5'
+      env: TOXENV=check_readme
     - python: '2.7'
       env: SELFINSTALL=1
     - python: '3.5'