Add support for non-karma exchange app owners as users.

Change the fb authentication mechanism to enable non-karma exchange app owners to use the karma-exchange app. 

Note: It appears the "/debug_token" facebook api call can only be made if the access token used for the call is an "app access token or a user access token that is an owner or developer of the app."

For search purposes, this was the error restFb was throwing:
Received Facebook error response of type OAuthException: (#100) You must provide an app access token or a user access token that is an owner or developer of the app