Let the code work on classes as well

[perdevpernull]

I suggest changing line 31
'- var prototype = Object.getPrototypeOf(object)

'+ var prototype;
switch (typeof object) {
case 'function': // class
prototype = object.prototype;
break;
case 'object': // instance of a class
prototype = Object.getPrototypeOf(object);
break;
default:
throw new Error('The argument has to be a class or an instance of a class.');
}