Add requirement to readme

README.md

@@ -2,6 +2,10 @@
 
 A zookeeper web administrator in node.js. It's based on [express.js](http://expressjs.com/) and [node-zookeeper](https://github.com/yfinkelstein/node-zookeeper).It will display zookeeper's data as a lazy loading tree,and display every path's stat info and data;and you can create,edit or delete path if you logon.
 
+##Requirement
+
+You must install node.js 0.4.x from https://github.com/joyent/node/tags and [npm](https://github.com/isaacs/npm).
+
 ##Configure
 First,you must install dependencies with npm