message: update weex events module
diff: import { updateListeners } from 'core/vdom/helpers/update-listeners'
  +let target: any
  +
  +function add (
  + event: string,
  + handler: Function,
  + once: boolean,
  + capture: boolean
  +) {
  + if (capture) {
  + console.log('Weex do not support event in bubble phase.')
  + return
  + }
  + if (once) {
  + const oldHandler = handler
  + const _target = target // save current target element in closure
  + handler = function (ev) {
  + const res = arguments.length === 1
  + ? oldHandler(ev)
  + : oldHandler.apply(null, arguments)
  + if (res !== null) {
  + remove(event, null, null, _target)
  + }
  + }
  + }
  + target.addEvent(event, handler)
  +}
  +
  +function remove (
  + event: string,
  + handler: any,
  + capture: any,
  + _target?: any
  +) {
  + (_target || target).removeEvent(event)
  +}
  +
  function updateDOMListeners (oldVnode: VNodeWithData, vnode: VNodeWithData) {
  if (!oldVnode.data.on && !vnode.data.on) {
  return
  }
  const on = vnode.data.on || {}
  const oldOn = oldVnode.data.on || {}
  - updateListeners(on, oldOn, (event, handler, capture) => {
  - if (capture) {
  - console.log('Weex do not support event in bubble phase.')
  - return
  - }
  - vnode.elm.addEvent(event, handler.bind(vnode.context))
  - }, (event) => {
  - vnode.elm.removeEvent(event)
  - }, vnode.context)
  + target = vnode.elm
  + updateListeners(on, oldOn, add, remove, vnode.context)
  }
  export default {
  