TODO(fejta): improve this documentation.

See:

• job.go for information about started.json and finished.json.
• junit subpackage for information about the junit files.
• prow, which typically creates these results.
  • In particular its pod utilities which create these files as testgrid expects them.

See documentation for pubsub and GCS' integration.

Testgrid can provide near realtime results by configuring GCS to send notifications of newly written results to a pubsub topic.

TODO(fejta): improve documentation, link to setup script.