Parse TAP results from pgtap

[rngadam]

app.json currently has the necessary stanzas to setup and run the tests:

      "scripts": {
        "test-setup": "./heroku-test-setup.sh",
        "test": "./test.sh $DATABASE_URL"
      }

pgtap runs and outputs TAP compatible output but only the exit code is considered for now.

these should be properly parsed by the Heroku CI

see: https://devcenter.heroku.com/articles/testpack-api