Reflect changes to the ServiceNow API

[RobinKnipe]

New changes:

• new endpoints:
  • https://lssitest.service-now.com/api/fho/siam_in/create_transaction (Test)
  • https://lssiprod.service-now.com/api/fho/siam_in/create_transaction (Prod)
• add ‘externalidentifier’ to change creation messages: "messageid": "HO_SIAM_IN_REST_CHG_POST_JSON", "external_identifier": " lev-ci-drone-service-now-99", "payload": "{\"title\":\"Deployment #99 of drone-service-now\",\"endTime\":\"2018-03-29 09:45:08\",\"description\":\"just a test\",\"supplierRef\":\"lev-ci-drone-service-now-99\"}"_
• HTTP response field ‘status’ is now named ‘transaction_status’ and will use:
  • ‘PROCESSED’ (Formerly ‘5’) and
  • ‘ERROR’ (Formerly ‘7’)

[RobinKnipe]

Fixed in version 0.0.2 (#17).