Facebook iOS SDK 3.7

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

    Upgrading from 3.6
     https://developers.facebook.com/docs/tutorial/iossdk/upgrading-from-3.6-to-3.7

Reviewed By: jacl

Test Plan: Release Testing.
Facebook iOS SDK 3.7.1

Summary:
    Bug fixes. See https://developers.facebook.com/ios/change-log-3.x/

Reviewed By: jacl

Test Plan: Release Testing.
Merge commit '99af010959325c6e26816623fc844cecef5f84db'

# By Chris Pan
# Via Chris Pan
* commit '99af010959325c6e26816623fc844cecef5f84db':
  Facebook iOS SDK 3.7.1
  Facebook iOS SDK 3.7