Support new picture field format

[revetkn]

Per Preston Crawford:

The Graph now returns images wrapped in a new JSON object. Have you seen this? Example.

https://graph.facebook.com/PrestonCrawford?fields=picture

{
   "id": "100002127094001",
   "picture": {
      "data": {
         "url": "http://profile.ak.fbcdn.net/hprofile-ak-snc6/186176_100002127094001_1594440109_q.jpg",
         "is_silhouette": false
      }
   }
}