[#8267] Add granted_at field to UserToken.
[#8267] Make UserToken.expiration_date nullable.
[#8267] Don't set user token expiration date by default.
[#8267] Wildcard fresh user tokens.
[close #8267] Fix get_access_token.
[close #8267] Exclude old tokens without expiration date.
Merge pull request #21 from Kern3l/master

#8267 Expiration date in Facebook tokens
[close #8199] Version Facebook call to /me.
Merge pull request #22 from Kern3l/master

[close #8199] Version Facebook call to /me.
[close #8200] Version debug_token API call.
Merge pull request #24 from Kern3l/debug-token-versioning

[close #8200] Version debug_token API call.
Merge branch 'master' of https://github.com/pozytywnie/django-facebook-auth