add installation in readme

readme.md

@@ -8,6 +8,16 @@ Description
 
 This plugin contains one text command names 'itodo' and a syntax definition with the same name.
 
+
+Installation
+------------------
+
+To install this plugin, you have two options:
+
+* Clone source code to Sublime Text 2 app folder, eg. ~/Library/Application Support/Sublime Text 2/iTodo.
+* If you have [Package Control](http://wbond.net/sublime_packages/package_control) installed, simply search for iTodo to install.
+
+
 Usage 
 ------------------
 
@@ -29,14 +39,15 @@ Highlight this item line and press "⌘ + d", it marks a tag "@done" and also ap
 	Project A:
 		+ call mum tomorrow at 8 am. @done (2012-01-08 18:12)
 
+[iTodo - Sublime Text 2上的GTD插件](http://gchen.cn/2012/01/gtd-with-itodo-in-sublime-text/)
 
 Contribution
 ------------------
 
 Thanks Taskmate for TextMate (https://github.com/svenfuchs/taskmate).
 
 
-Source / Installation 
+Source code and support 
 ------------------
 
 https://github.com/chagel/itodo