Destructible v5.2.0-alpha.6

• Errored propagation through destruct channel. Closes #163.
• Always call _destroy internally, not destroy. Closes #162.
• Remove Delay dependency.
• Notes on scrammable, minor code tidy. Closes #146.
• Remove user scrammable. See #146.
• Remove context passed to _destroy. Closes #160.
• Add sub-destructible error in catch block. See #160.

Closes #164.