function proxiedComponentWillUnmount() {
	    var index = mountedInstances.indexOf(this);
	    // Unless we're in a weird environment without componentDidMount
	    if (index !== -1) {
	      mountedInstances.splice(index, 1);
	    }
	    if (typeof current.componentWillUnmount === 'function') {
	      return current.componentWillUnmount.apply(this, arguments);
	    }
	  }
Augments the original componentWillUnmount with instance tracking.