Error creating box with a THREE.Audio in the tree

[mqp]

Unfortunately, it doesn't seem to be safe to call clone on an arbitrary three.js Object3D. As a result, creating a box shape fails if you try to create it on an object hierarchy that includes somewhere in it an Audio or PositionalAudio Object3D. For example, in a browser:

const listener = new THREE.AudioListener();
const object = new THREE.Mesh(new THREE.BoxGeometry(10, 10, 10));
object.children.push(new THREE.Audio(listener));

// fails
const box = mesh2shape(object, { type: mesh2shape.Type.BOX });

will result in

TypeError: listener is undefined three.js:39118
	Audio three.js:39118
	clone three.js:8636
	copy three.js:8674
	clone three.js:8636
	createBoundingBoxShape index.js:104
	mesh2shape index.js:25

This regressed recently with this commit: 0c7bc98

I don't know enough about three.js conventions to say whether three or this library is the one that is "wrong". One possible fix would be to write the bounding box creation code in question directly in terms of the matrices involved instead of calling clone, but it looks like that would be mostly duplicating a lot of code from Box3.

[mqp]

Ah, this is what my esteemed colleague @johnshaughnessy has made a PR to try to fix: #12