remove upgrade docker on travis.

Signed-off-by: Bo-Yi Wu <[email protected]>

Author: appleboy

.travis.yml

@@ -6,25 +6,15 @@ services:
   - docker
 
 go:
-  - 1.5
-  - 1.6
+  - 1.5.4
   - 1.6.3
+  - 1.7.1
   - tip
 
 env:
   global:
-    - DOCKER_COMPOSE_VERSION=1.7.1
     - secure: 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
 
-before_install:
-  - sudo apt-get -y update
-  - sudo apt-get -y purge docker-engine
-  - sudo apt-get -y install docker-engine
-  - 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
-  - chmod +x docker-compose
-  - sudo mv docker-compose /usr/local/bin
-
 install:
   - export GO15VENDOREXPERIMENT=1
   - go get github.com/mattn/goveralls