Release Destructible version 7.0.0-alpha.37.
Release Destructible version 7.0.0-alpha.37.

 * Test awaiting `done`.
 * Tidy sub-destructible option parsing.
 * Test set sub-destructible timeout.
 * Test rescue of a promise.
 * Destroy deferrables if errored.
 * Ephemeral timer takeover.
 * On error return for sub-destructibles.
 * Use Future in shutdown.
 * New constructor arguments.
 * Remove trace function check.
 * Remove `exceptional`.
 * Auto-destroy rescue, remove terminal.

Closes #253.

bigeasy/destructible