Pointsman 0.13.1

The GitHub connector checks the engine's answer before it acts, and never acts on a test decision (#193).

For deployments:

• Move ref in engine.json to the commit of v0.13.1. No migration, no new secrets, no new permissions.

What changed:

• The engine's answer is checked once, for both the HTTP adapter and the service binding: decision_id (a UUID), action (an action name), profile and ref (the ones asked for), profile_version, rule, and facts, review and test when present must have the right shape. A decision kept for once_per_head is checked again before it is reused. An answer that does not fit is an invalid answer.
• Test decisions are never acted on: a decision with test: true (made with a test token) does nothing.
• For an invalid answer or a test decision the connector does nothing (no approve, keep_approval, comment, label or reviewer request), keeps nothing, sends nothing on through requires and schedules no recheck. In a profile that maps approve, an approval of the head commit is withdrawn, as for any decision that does not keep it. For a test decision the check run also says to use a token made without --test. The check run is neutral and says invalid answer: nothing done or test decision: nothing done; the log names the field, never its value. It is not retried; the next event asks again.
• A 2xx body that is not JSON (HTTP) or not an object (binding) used to be retried; it is now an invalid answer.