Display file:// uri instead of meaningless schema identifier in messages

Changes messages from:
> The property '#/groups' did not contain a minimum number of items 12 in schema a34e5f16-0210-5608-836b-8df681d5346a#

to:
> The property '#/groups' did not contain a minimum number of items 12 in schema file:///Users/Thoughtworker/repos/rackspace/polytrix/pacto/contracts/ord.autoscale.api.rackspacecloud.com/v1.0/_tenant_id/groups.json#response

I did think about adding a little hack to put the fragment `#response` there as well, but it's a bit too hacky.  json-schema won't display the fragment from the URI.