Updated Facebook provider to support "auth_type" in the login dialogue.

I just made a small update to the Facebook provider to support the "auth_type" parameter in the login dialogue.

The provider will also automatically generate an "auth_nonce" if "auth_type" is present. It will then check the nonce when Facebook redirects back to HybridAuth.

More info about the feature here: http://developers.facebook.com/docs/howtos/login/server-side-re-auth/