code: function createVirtualDomNode(el, attr) {
  	var ns = el.namespaceURI !== HTML_NAMESPACE ? el.namespaceURI : null;
  	var key = attr && el.getAttribute(attr) ? el.getAttribute(attr) : null;
  
  	return new VNode(
  		el.tagName
  		, createProperties(el)
  		, createChildren(el, attr)
  		, key
  		, ns
  	);
  }
docs: Create vnode from dom node
  
  @param   Object  el    DOM element
  @param   String  attr  Attribute name that contains vdom key
  @return  Object        VNode