Advancing Ticket Auth to more interoperable implementations

@dshanske and I are going to be working on TicketAuth implementations. From the draft specification:

Ticket Auth is an extension to IndieAuth that enables a publisher to send authorization, known as a ticket, that can be redeemed for an access token. This allows both solicited and unsolicited invitations to fetch restricted resources.

If anyone is interested in independently implementing the spec along with us, please respond here!