Merge pull request #6694 from gyuho/travis

travis: test with Go 1.7.3

.travis.yml

@@ -4,7 +4,7 @@ go_import_path: github.com/coreos/etcd
 sudo: false
 
 go:
-  - 1.7.1
+  - 1.7.3
   - tip
 
 env: