message: [changelog] 1.6.7
diff: ## Changelog
  +## [v1.6.7](https://github.com/youzan/vant/tree/v1.6.7)
  +`2019-02-26`
  +
  +**Improvements**
  +
  +- Button: add loading-size prop [\#2854](https://github.com/youzan/vant/pull/2854)
  +- Icon: optimzie round corner of some icons [\#2856](https://github.com/youzan/vant/pull/2856)
  +- Sku: Add custom settings in stepper stock [\#2839](https://github.com/youzan/vant/pull/2839)
  +- Stepper: add focus event [\#2841](https://github.com/youzan/vant/pull/2841)
  +
  +**Bug Fixes**
  +
  +- fix Actionsheet lazy-render not work [\#2840](https://github.com/youzan/vant/pull/2840)
  +- fix Actionsheet get-container not work [\#2853](https://github.com/youzan/vant/pull/2853)
  +- fix Tab should scroll to active tab when inited [\#2857](https://github.com/youzan/vant/pull/2857)
  +- fix Checkbox uncheckable when inside cell [\#2855](https://github.com/youzan/vant/pull/2855)
  +- fix CouponList incorrectly render when disabled list empty [\#2845](https://github.com/youzan/vant/pull/2845)
  +
  +
  ## [v1.6.6](https://github.com/youzan/vant/tree/v1.6.6)
  `2019-02-24`
  