Fix the link of Travis-CI build status icon

Author: dinever

README.md

@@ -2,7 +2,7 @@
 
 ![Dingo Logo](https://cloud.githubusercontent.com/assets/1311594/15427334/652081ae-1e62-11e6-9ae3-1dd0a667f22d.png)
 
-[![CI status](https://img.shields.io/travis/dingoblog/dingo.svg)]()
+[![CI status](https://img.shields.io/travis/dingoblog/dingo.svg)](https://travis-ci.org/dingoblog/dingo/)
 [![Gitter](https://badges.gitter.im/dingoblog/dingo.svg)](https://gitter.im/dingoblog/dingo?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)
 
 Dingo is a full-featured blog engine written in Go.