install gocheck on travis

.travis.yml

@@ -18,5 +18,8 @@ before_script:
   - tar -xzf elasticsearch-${ES_VERSION}.tar.gz -C ${HOME}/elasticsearch
   - ${HOME}/elasticsearch/elasticsearch-${ES_VERSION}/bin/elasticsearch >/dev/null &
 
+install:
+  - go get gopkg.in/check.v1
+
 script:
   - make test