message: [changelog] 0.12.10
diff: ## Changelog
  +### [0.12.10](https://github.com/youzan/vant/tree/v0.12.10)
  +`2018-02-12`
  +
  +**Improvements**
  +
  +* add build-in style document [\#633](https://github.com/youzan/vant/pull/633) [@chenjiahan](https://github.com/chenjiahan)
  +* Checkbox: optimzie DOM struct [\#636](https://github.com/youzan/vant/pull/636) [@chenjiahan](https://github.com/chenjiahan)
  +* Checkbox: support config the maximum amount of checked options [\#631](https://github.com/youzan/vant/pull/631) [@mpandar](https://github.com/mpandar)
  +
  +**Bug Fixes**
  +
  +* Stepper: change event error when clear input [\#635](https://github.com/youzan/vant/pull/635) [@chenjiahan](https://github.com/chenjiahan)
  +
  +
  ### [0.12.9](https://github.com/youzan/vant/tree/v0.12.9)
  `2018-02-08`
  