Update .travis.yml

Author: mshandrovskiy

.travis.yml

@@ -1,10 +1,10 @@
 language: python
 python:
-  - "3.6"
+  - "3.6.6"
 # command to install dependencies
 install:
   - pip install -r requirements-dev.txt
 # command to run tests
 script:
   - flake8 sdiff tests
-  - nosetests
+  - nosetests