Update README.md

lewis liu · lewis liu · commit dfffa097345d · 2016-02-18T11:08:41.000+08:00
diff --git a/README.md b/README.md
@@ -5,6 +5,8 @@
 
 [angular2系列教程（三）components](http://www.cnblogs.com/lewis617/p/5195223.html)
 
+[angular2系列教程（四）Attribute directives](http://www.cnblogs.com/lewis617/p/5197481.html)
+
 连载中……
 
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