Merge pull request alibaba#1615 from alibaba/doc-feature-playground

* [doc] update playground doc

Author: Jinjiang

doc/tools/playground-app.md

@@ -4,15 +4,14 @@ Weex Playground App
 
 One of best parts of Weex is Native Runtime . After preview your `we file` render in H5 using weex-toolkit CLI , you can try Native Runtime in a standalone App , this is Weex Playground App . More then that ,Weex playground App preset  a lot of  Demo & ShowCase ,so you will get to experience  performance of Weex native runtime  easily.
 
-Android version of Playground App can be downloaded [here](http://alibaba.github.io/weex/download.html).  iOS version will soon be ready to download.
-
+Android and IOS version of Playground App can be downloaded [here](http://alibaba.github.io/weex/download.html).
 
 ## Screenshot 
 
-![Weex playground App](http://gtms01.alicdn.com/tps/i1/TB1bC5LMpXXXXb7XXXXA0gJJXXX-720-1280.png)
+![Weex playground App](http://gw.alicdn.com/mt/TB1AoPdOXXXXXcXapXXXXXXXXXX-720-1280.png)
 
 
-This is main interface of Weex Playground App , grey color list item is Demo/Showcase entry . click top right  corner Icon will active QR scaner that  work with Weex [toolkit CLI](../tools/cli.md)
+This is main interface of Weex Playground App , you can click the item to see the corresponding demo  . click top right  corner Icon will active QR scaner that  work with Weex [toolkit CLI](../tools/cli.md)
 
 please refer to [Weex Tutorial](../tutorial.md)