Save token expiration date in authenticate.
Save token expiration date in authenticate.

Change-Id: I0aadbe06b2e55c4591b0818059e3ac4b1f34010e
Reviewed-on: http://review.pozytywnie.pl:8080/8182
Tested-by: Jenkins
Reviewed-by: Tomasz Wysocki <f17c2dc043305c950a029074ababd304e0373387@gmail.com>

pozytywnie/django-facebook-auth,pozytywnie/django-facebook-auth,jgoclawski/django-facebook-auth,jgoclawski/django-facebook-auth