message: [changelog] 1.5.6
diff: ## Changelog
  +## [v1.5.6](https://github.com/youzan/vant/tree/v1.5.6)
  +`2019-01-22`
  +
  +**Improvements**
  +
  +- Card: add origin-price slot [\#2588](https://github.com/youzan/vant/pull/2588)
  +- Switch: add active-value & inactive-value prop [\#2590](https://github.com/youzan/vant/pull/2590)
  +- SwitchCell: add active-value & inactive-value prop [\#2591](https://github.com/youzan/vant/pull/2591)
  +
  +**Bug Fixes**
  +
  +- fix Card: centered prop not work [\#2589](https://github.com/youzan/vant/pull/2589)
  +- fix Icon name not work when passing url [\#2585](https://github.com/youzan/vant/pull/2585)
  +
  +
  ## [v1.5.5](https://github.com/youzan/vant/tree/v1.5.5)
  `2019-01-21`
  