Add 'Collegiate - Learn Anywhere' to the showcase

Summary:Added Collegiate, an app that lets you learn from world's best colleges for free. Collegiate includes 650+ courses from MIT, Stanford, Yale, Berkeley, IIT Madras. The app is completely built using react native.
Closes https://github.com/facebook/react-native/pull/6033

Differential Revision: D2958238

fb-gh-sync-id: e55fed11e7fbef22552377e77359195c573bdd05
shipit-source-id: e55fed11e7fbef22552377e77359195c573bdd05

website/src/react-native/showcase.js

@@ -217,6 +217,12 @@ var apps = [
     link: 'https://www.codementor.io/downloads',
     author: 'Codementor',
   },
+  {
+    name: 'Collegiate - Learn Anywhere',
+    icon: 'http://a3.mzstatic.com/us/r30/Purple69/v4/17/a9/60/17a960d3-8cbd-913a-9f08-ebd9139c116c/icon175x175.png',
+    link: 'https://itunes.apple.com/app/id1072463482',
+    author: 'Gaurav Arora',
+  },
   {
     name: 'Company name search',
     icon: 'http://a4.mzstatic.com/us/r30/Purple69/v4/fd/47/53/fd47537c-5861-e208-d1d1-1e26b5e45a36/icon350x350.jpeg',