Fix mailer specs on latest rails

Mailer methods are not evaluated anymore unless you call body or deliver
on the return message object
less hacky log entries check on specs
AR#reflections keys are strings as of rails 4.2
Fix order.can_cancel test set up

They probably only passed before because rails would not always
typecast strings to db columns strings. e.g.

        order.shipment_state = :ready
        order.shipment_state
        => :ready

        as of rails 4.2

        order.shipment_state = :ready
        order.shipment_state
        => "ready"