增加dubbo下载地址

README.md

@@ -114,6 +114,7 @@ zheng
 * ActiveMQ [http://activemq.apache.org/download-archives.html](http://activemq.apache.org/download-archives.html "ActiveMQ")
 * ZooKeeper [http://www.apache.org/dyn/closer.cgi/zookeeper/](http://www.apache.org/dyn/closer.cgi/zookeeper/ "ZooKeeper")
 * Jenkins [http://updates.jenkins-ci.org/download/war/](http://updates.jenkins-ci.org/download/war/ "Jenkins")
+* Dubbo [http://www.apache.org/dyn/closer.cgi/zookeeper/](http://dubbo.io/Download-zh.htm "Dubbo")
 
 # 数据模型
 ![数据库模型](project-datamodel/zheng.png)