rewrite `parent` and `find` method for jqLite

jqLite.extra.js

angular.$ = angular.element;

// jqLite `.parent([selector])` 支持 selector
angular.$.prototype.parent = function(sel) {
  if(!sel) return angular.$(this[0].parentNode);
  var list = [].slice.call(document.querySelectorAll(sel))
    , currentNode = this[0]
    , ret;

  while(currentNode.nodeName !== 'HTML') {
    currentNode = currentNode.parentNode;
    var index = list.indexOf(currentNode);
    if(index !== -1) {
      ret = currentNode;
      currentNode = document.documentElement;
      continue;
    }
  }
  return angular.$(ret);
}

// jqLite `.find([selector])` 支持 selector
angular.$.prototype.find = function(sel) {
  if(!sel) return angular.$();
  var list = [].slice.call(document.querySelectorAll(sel))
    , childrens = [].slice.call(this[0].getElementsByTagName('*'))
    , ret = [];

  list.forEach(function(el) {
    if(childrens.indexOf(el) !== -1) ret.push(el);
  })

  return angular.$(ret);
}

@exherb 写 UI 组件的时候会非常多用到。