code: function _matchesSelector (element, selector, boundElement) {
    // no selector means this event was bound directly to this element
    if (selector === '_root') {
      return boundElement;
    }
  
    // if we have moved up to the element you bound the event to
    // then we have come too far
    if (element === boundElement) {
      return;
    }
  
    if (_getMatcher(element).call(element, selector)) {
      return element;
    }
  
    // if this element did not match but has a parent we should try
    // going up the tree to see if any of the parent elements match
    // for example if you are looking for a click on an <a> tag but there
    // is a <span> inside of the a tag that it is the target,
    // it should still work
    if (element.parentNode) {
      _level++;
      return _matchesSelector(element.parentNode, selector, boundElement);
    }
  }
docs: determines if the specified element matches a given selector
  
  @param {Node} element - the element to compare against the selector
  @param {string} selector
  @param {Node} boundElement - the element the listener was attached to
  @returns {void|Node}