Facebook Android SDK 3.8

Summary: Facebook Android SDK 3.8 (see https://developers.facebook.com/docs/android/change-log-3.x/)

Test Plan: Built ZIP

Reviewers: mingfli

Reviewed By: mingfli

CC: subodh

Differential Revision: https://phabricator.fb.com/D1237186
Merge tag 'sdk-version-3.8.0' into master-no_appcompat

SDK 3.8.0