Fix travis

.travis.yml

@@ -5,7 +5,6 @@ go:
   - 1.3
   - 1.4
   - 1.5
-  - tip
 
 services:
   - docker
@@ -14,6 +13,7 @@ before_install:
     - curl -L https://github.com/docker/compose/releases/download/1.4.2/docker-compose-`uname -s`-`uname -m` > docker-compose
     - chmod +x docker-compose
     - sudo mv docker-compose /usr/local/bin
+    - go get golang.org/x/tools/cmd/cover
     - sed -i -e 's/golang/golang:'"$TRAVIS_GO_VERSION"'/' docker-compose.yml
 
 script: make test