Add instagram to docs

Author: loopj

index.md

@@ -35,7 +35,7 @@ Features
 Who is Using It?
 ----------------
 [Instagram](https://play.google.com/store/apps/details?id=com.instagram.android)
-:   #1 photo app on android, over 10million users
+:   Instagram is the #1 photo app on android, with over 10million users
 
 [Heyzap](https://market.android.com/details?id=com.heyzap.android)
 :   Social game discovery app with millions of users