After discussing, we've decided it makes more sense to include it. We're
already forwarding every conflicting method to `to_a`, and there's no
conflation of concerns. `Enumerable` has no mutating methods, and it
just allows us to simplify the code. No existing methods will have a
change in behavior. Un-overridden Enumerable methods will simply
delegate to `each`.

[Sean Griffin & bogdan]