aerogear-ios-oauth2 is not able to get the auth token from Facebook.

The problem seems that the SDK targets API 2.2 which is now deprecated and 2.4 (min allowed at the moment) returns the auth token in a JSON response, which makes this code useless
https://github.com/aerogear/aerogear-ios-oauth2/blob/master/AeroGearOAuth2/FacebookOAuth2Module.swift#L50-L69

We should target API 2.10 as it's latest at the moment.