Bugfix: User#where now takes options into account

This is needed [for remote sign-out to work properly][1].

[1]: https://github.com/alphagov/gds-sso/blob/master/lib/gds-sso/warden_config.rb#L30
Merge pull request #130 from alphagov/bugfix-remote-signout

Bugfix to remote sign-out after gds-sso version bump