following v1.1.0

Following

<div class="ad-container">
  <div data-following-mark="{{feelback}}">
    ad content
  </div>
</div>

const following = new Following({
  container: <String|Element>, // 广告容器
  viewport: <String|Elmeent>, // 视口，不传，则默认 container 为视口,
  selectTag: <String>, // 广告item的属性, 默认为 'data-following-mark'
  eventSource: <Element|Array[Element]> // 事件源，会监听 scroll, resize 事件
})
following.rescan() // 有新的渲染，需要执行
following.triggerScroll() // 手动触发曝光检测

following.on(Following.EVENT_IMPRESSIONEND, function(type, el, feelback, adid, fbgroupindex){
  // todo
})