.travis.yml in docker-api-1.24.1 vs .travis.yml in docker-api-1.25.0

- old
+ new

@@ -1,10 +1,18 @@
 sudo: required
-services:
-  - docker
+dist: trusty
 cache: bundler
 language: ruby
 rvm:
   - 1.9.3
   - 2.0
   - 2.1
   - 2.2
+env:
+  - DOCKER_VERSION=1.6.2
+  - DOCKER_VERSION=1.7.1
+  - DOCKER_VERSION=1.8.3
+  - DOCKER_VERSION=1.9.1
+before_install: ./script/install_dependencies.sh
+before_script:
+ - export PATH=/opt/docker:$PATH
+ - docker version