message: [changelog] 1.6.0
diff: ## Changelog
  +## [v1.6.0](https://github.com/youzan/vant/tree/v1.6.0)
  +`2019-02-04`
  +
  +**Breaking changes**
  +
  +- Radio: refactored, now has the same stuct as Checkbox [\#2651](https://github.com/youzan/vant/pull/2651)
  +
  +**Improvements**
  +
  +- Use JSX to rewrite all components
  +- Transform part components to functional for better performance
  +- Card: add tag slot [\#2636](https://github.com/youzan/vant/pull/2636)
  +- Icon: add weapp-nav icon [\#2682](https://github.com/youzan/vant/pull/2682)
  +- Radio: add icon slot [\#2651](https://github.com/youzan/vant/pull/2651)
  +- Radio: add shape prop [\#2651](https://github.com/youzan/vant/pull/2651)
  +- Toast: add className prop [\#2680](https://github.com/youzan/vant/pull/2680)
  +- Notify: add className prop [\#2681](https://github.com/youzan/vant/pull/2681)
  +- Popup: add open/close event [\#2649](https://github.com/youzan/vant/pull/2649)
  +- Popup: add opened/closed event [\#2650](https://github.com/youzan/vant/pull/2650)
  +
  +**Bug Fixes**
  +
  +- fix ContactList button position [\#2634](https://github.com/youzan/vant/pull/2634)
  +- fix Toast clear in multiple mode [\#2635](https://github.com/youzan/vant/pull/2635)
  +- fix SwipeCell maximum left offset [\#2633](https://github.com/youzan/vant/pull/2633)
  +- fix Popup get-container error when destoryed [\#2679](https://github.com/youzan/vant/pull/2679)
  +
  +
  ## [v1.5.7](https://github.com/youzan/vant/tree/v1.5.7)
  `2019-01-24`
  