Facebook iOS SDK 3.13

Summary:
    see https://developers.facebook.com/ios/change-log-3.x/

Upgrading:
    https://developers.facebook.com/docs/ios/upgrading/
Facebook iOS SDK 3.13.1

Summary:
    see https://developers.facebook.com/ios/change-log-3.x/

Upgrading:
    https://developers.facebook.com/docs/ios/upgrading/
Merge remote-tracking branch 'upstream/master'

* upstream/master:
  Facebook iOS SDK 3.13.1
  Facebook iOS SDK 3.13