move contents to ticket description

before this change, the body of the ticket was created as a ticket comment
in Zendesk. This meant that the text was in the "ticket_audit" resource,
instead of the "ticket" resource in Zendesk world. Now it is the ticket
description.

This change brings the support app in line with the feedback app in this respect.
Merge pull request #63 from alphagov/move-contents-to-ticket-description

move contents to ticket description