Add "SAY a Short Video Community" app to the showcase.

Summary:
SAY is "Q & A community-based short video", All based react native development

- You can shoot video
- Video Filters can be switched
- Private chat

![image](https://cloud.githubusercontent.com/assets/18495/15239741/7a1152be-1917-11e6-9c93-0e75b3a7bd60.png)

![image](https://cloud.githubusercontent.com/assets/18495/15239758/ae7a08c0-1917-11e6-82ea-f0f998785bd6.png)

![image](https://cloud.githubusercontent.com/assets/18495/15239776/c89b5588-1917-11e6-8962-5803865a02b4.png)

![image](https://cloud.githubusercontent.com/assets/18495/15239783/d0500670-1917-11e6-9699-708b1d9ebceb.png)
Closes https://github.com/facebook/react-native/pull/7547

Differential Revision: D3297728

fbshipit-source-id: 3ef57a8042c5de34d56ce4fcde1b62cccbb3f422

website/src/react-native/showcase.js

@@ -765,6 +765,12 @@ var apps = [
     linkPlayStore: 'https://play.google.com/store/apps/details?id=kr.dobbit.sharehows',
     author: 'Dobbit Co., Ltd.'
   },
+  {
+    name: 'SAY',
+    icon: 'http://a1.mzstatic.com/us/r30/Purple30/v4/ee/d8/b3/eed8b3e5-c55d-bc97-7228-2bfb4323ddef/icon175x175.png',
+    link: 'https://itunes.apple.com/us/app/id1069693851',
+    author: 'beijing qingfengyun Technology Co., Ltd.',
+  },
   {
     name: 'ShareWis',
     icon: 'https://s3-ap-northeast-1.amazonaws.com/sw-misc/sharewis3_app.png',