Update fb login feature{Issue:FB OAuth2(callback:=>invalid_credentials)}

Add the omniauth failure inspector. The error of "invalid_credentials" is actually depending on OAuth callback operation between the "Cross-Site Request Forgery" validation feature on FB OAuth's provider and OAuth's operation of [omniauth-facebook](https://github.com/cmer/omniauth-facebook/tree/rollback-omniauth-oauth2) library. 
Can you repair it? 

When we see the Auth Hash, we got that the token are expired and it has not been renew token again from the FB?
[Here](https://gist.github.com/stevebourne/2394427) may be the answer?? 
Can you repair it?