message: [changelog] 1.6.12
diff: ## Changelog
  +## [v1.6.12](https://github.com/youzan/vant/tree/v1.6.12)
  +`2019-03-28`
  +
  +**Improvements**
  +
  +- Actionsheet: add less vars [\#3049](https://github.com/youzan/vant/pull/3049)
  +
  +**Bug Fixes**
  +
  +- fix SwipeCell unable to scroll page when opened [\#3056](https://github.com/youzan/vant/pull/3056)
  +- fix Picker render error when set data async [\#3064](https://github.com/youzan/vant/pull/3064)
  +- fix Button square prop not work when use hairline [\#3058](https://github.com/youzan/vant/pull/3058)
  +
  +
  ## [v1.6.11](https://github.com/youzan/vant/tree/v1.6.11)
  `2019-03-22`
  