Support check, reset, and fingerprint for tokens

[Check](https://developer.github.com/v3/oauth_authorizations/#check-an-authorization) and [reset](https://developer.github.com/v3/oauth_authorizations/#reset-an-authorization) would be useful for token manipulating applications now that the new token API limitations are in place. Also, exposure of the `fingerprint` property in the `Github_t.auth` type would be nice.
