message: [Deprecate] add Waterfall deprecate tip
diff: import Waterfall from './directive.js';
  const install = function(Vue) {
  + if (process.env.NODE_ENV !== 'production') {
  + console.warn('[Vant warn] Waterfall is deprecated, please use List component instread.');
  + }
  Vue.directive('WaterfallLower', Waterfall('lower'));
  Vue.directive('WaterfallUpper', Waterfall('upper'));
  };
  