Merge pull request #545 from auchri/patch-1

Update .travis.yml

.travis.yml

@@ -4,7 +4,7 @@ services:
 
 env:
     global:
-        - DOCKER_VERSION=1.10.1-0~trusty
+        - DOCKER_VERSION=1.12.1-0~trusty
 
 before_install:
   # list docker-engine versions