Adding config to allow Facebook auth to trust forwarded sessions

This change relies on hybridauth pull request https://github.com/hybridauth/hybridauth/pull/159
Problem is described here: https://github.com/hybridauth/hybridauth/issues/155
Fixed coding style
Merge pull request #143 from jeffery/fix-facebook-trust-forwarded-sessions

Adding config to allow Facebook auth to trust forwarded sessions