Load user from token, not from username
ShibbolethUserProviderInterface now includes loadUser($token) method
AbstractShibbolethUserProvider includes simple implementation of loadUser($token)

This modification enables updating user object (stored elsewhere) with data from shibboleth headers
Safety check
Make sure user provider implements ShibbolethUserProviderInterface before using loadUser($token) method.
Fallback to loadUserByUsername($username) otherwise
Fixed typo
Merge pull request #6 from rejsmont/master

Load user from token in AuthProvider when using UserProvider implementing ShibbolethUserProviderInterface.