message: [changelog] 0.12.3
diff: ## Changelog
  +### [0.12.3](https://github.com/youzan/vant/tree/v0.12.3)
  +
  +`2018-01-12`
  +
  +**Improvements**
  +
  +* NavBar: add zIndex prop [\#525](https://github.com/youzan/vant/pull/525) [@chenjiahan](https://github.com/chenjiahan)
  +* Cell: adjust right padding of arrow [\#531](https://github.com/youzan/vant/pull/531) [@chenjiahan](https://github.com/chenjiahan)
  +
  +**Bug Fixes**
  +
  +* Area: should valid data before get area list [\#520](https://github.com/youzan/vant/pull/520) [@chenjiahan](https://github.com/chenjiahan)
  +* AddressEdit: setAreaCode now work [\#524](https://github.com/youzan/vant/pull/524) [@chenjiahan](https://github.com/chenjiahan)
  +* Picker: change event not triggered when click option [\#532](https://github.com/youzan/vant/pull/532) [@chenjiahan](https://github.com/chenjiahan)
  +* PullRefresh: only triggered when drag in vertical direction [\#521](https://github.com/youzan/vant/pull/521) [@ZhiRuYan](https://github.com/ZhiRuYan)
  +
  ### [0.12.2](https://github.com/youzan/vant/tree/v0.12.2)
  `2018-01-08`
  