Update docker for travis.

Author: viferga

.travis.yml

@@ -38,6 +38,11 @@ env:
     - IMAGE_NAME: registry.hub.docker.com/$TRAVIS_REPO_SLUG
     - ARTIFACTS_PATH: $TRAVIS_BUILD_DIR/artifacts
 
+addons:
+  apt:
+    packages:
+      - docker-ce
+
 before_install:
   - sudo rm /usr/local/bin/docker-compose
   - curl -L https://github.com/docker/compose/releases/download/${DOCKER_COMPOSE_VERSION}/docker-compose-`uname -s`-`uname -m` > docker-compose