message: [changelog] 1.5.7
diff: ## Changelog
  +## [v1.5.7](https://github.com/youzan/vant/tree/v1.5.7)
  +`2019-01-24`
  +
  +**Improvements**
  +
  +- add live icon
  +- add lock icon
  +- add audio icon
  +- add column icon
  +- add replay icon
  +- add shrink icon
  +- add graphic icon
  +- add invition icon
  +- add ascending icon
  +- add descending icon
  +- add play-circle icon
  +- add stop-circle icon
  +- add pause-circle icon
  +- add play-circle-o icon
  +- add stop-circle-o icon
  +- add pause-circle-o icon
  +- Field: add click-left-icon event [\#2605](https://github.com/youzan/vant/pull/2605)
  +
  ## [v1.5.6](https://github.com/youzan/vant/tree/v1.5.6)
  `2019-01-22`
  