chore: Update travis to support docker

Author: sijis

.travis.yml

@@ -1,13 +1,21 @@
-sudo: false
+sudo: required
+services:
+  - docker
 language: python
-python:
-  - "2.7"
-env:
-    - TOX_ENV=flake8
-    - TOX_ENV=py27
-    - TOX_ENV=py26
+matrix:
+  include:
+    - python: 2.6
+      env: TOXENV=py26
+    - python: 2.7
+      env: TOXENV=py27
+    - python: 3.5
+      env: TOXENV=py35
+    - python: 3.6
+      env: TOXENV=py36
+    - python: 3.6
+      env: TOXENV=flake8
+
 install:
     - pip install tox
 script:
     - tox -e $TOX_ENV
-