Ckozak/guestid subresource

guest resource path is /consumers/{consumer_uuid}/guestids.
The resource allows PUT to the base with a list of guestId json, as well
as PUT and DELETE to /consumers/{consumer_uuid}/guestids/{guest_id}
to create/modify/delete a single guest per hypervisor event.

DELETE on a single GuestId has the option to also unregister
a registered consumer if permissions allow

Updated candlepin_api.rb to support the new resource/features
Added spec tests for new features, taking advantage of the new
api methods