Function: removeSubview
Removes <Barefoot.View> from this view (if present as subview) and sets the
former subviews parentView property to undefined.

Parameters:
(Barefoot.View) subview - A <Barefoot.View> subview to remove from this
view
function removeSubview(subview) {
	debug('remove subview `%s`', this.toString());
	subview.close();

	if(this.subviews) {
		this.subviews = _.without(this.subviews, subview);
	}

	subview.parentView = undefined;
}