message: [changelog] 0.12.9
diff: ## Changelog
  +### [0.12.9](https://github.com/youzan/vant/tree/v0.12.9)
  +`2018-02-08`
  +
  +**Improvements**
  +
  +* PullRefresh: add refersh event [\#625](https://github.com/youzan/vant/pull/625) [@chenjiahan](https://github.com/chenjiahan)
  +* Circle: optimzie linecap [\#624](https://github.com/youzan/vant/pull/624) [@chenjiahan](https://github.com/chenjiahan)
  +* Picker: add loading prop [\#619](https://github.com/youzan/vant/pull/619) [@chenjiahan](https://github.com/chenjiahan)
  +* Loading: add size prop [\#620](https://github.com/youzan/vant/pull/620) [@chenjiahan](https://github.com/chenjiahan)
  +* Loading: add circular type [\#618](https://github.com/youzan/vant/pull/618) [@chenjiahan](https://github.com/chenjiahan)
  +* Loading: change default type to circular [\#623](https://github.com/youzan/vant/pull/623) [@chenjiahan](https://github.com/chenjiahan)
  +
  +**Bug Fixes**
  +* fix Sku message observation [\#627](https://github.com/youzan/vant/pull/627) [@w91](https://github.com/w91)
  +
  ### [0.12.8](https://github.com/youzan/vant/tree/v0.12.8)
  `2018-02-07`
  