message: [changelog] 1.6.17
diff: ## Changelog
  +## [1.6.17](https://github.com/youzan/vant/tree/v1.6.17)
  +`2019-05-05`
  +
  +**Improvements**
  +
  +- List: add direction prop [\#3223](https://github.com/youzan/vant/pull/3223)
  +- Cell: add title-style prop [\#3233](https://github.com/youzan/vant/pull/3233)
  +- Field: add label-width prop [\#3235](https://github.com/youzan/vant/pull/3235)
  +
  +**Bug Fixes**
  +
  +- fix Card thumb image align center [\#3229](https://github.com/youzan/vant/pull/3229)
  +- fix Icon new and question icon incomplete render
  +- fix Step text display overlapping in small screen devices
  +- fix Step incorrect active step when insert step asynchronously
  +- fix Popup click-overlay event triggered twice when show multiple popup
  +
  +
  ## [v1.6.16](https://github.com/youzan/vant/tree/v1.6.16)
  `2019-04-26`
  