Update smarty streets results coordinates method to return nil when both latitude and longitude do not exist

SmartyStreets is permanently changing their ZIP Code API endpoint by
June 22 at 9am Mountain Time.  The legacy API endpoint is available
until the 22nd.

This change basically changes the API endpoint and updated the tests to
reflect the change.

Test was failing for irrelevant reasons.

To run a single file, use:

  ruby -I test <filename>

This should have been part of bd37a240.

Also much code cleanup.