增加 gitter badge

Author: JamesZBL

README.md

@@ -3,7 +3,7 @@
 
 [![License MIT](https://img.shields.io/badge/license-MIT-blue.svg)](https://github.com/JamesZBL/java_design_patterns/blob/master/LICENSE)
 [![Build status](https://travis-ci.org/JamesZBL/java_design_patterns.svg?branch=master)](https://travis-ci.org/JamesZBL/java_design_patterns)
-
+[![Gitter](https://img.shields.io/gitter/room/nwjs/nw.js.svg)](https://gitter.im/java_design_patterns/)
 ## 介绍
 
 设计模式（Design pattern）是用于面向对象程序设计的、有效提高代码重用效率、有着明确使用场景分类的程序设计规范的总结。使用设计模式的