message: [changelog] 0.11.8
diff: ## Changelog
  +### [0.11.8](https://github.com/youzan/vant/tree/v0.11.8)
  +`2017-12-08`
  +
  +**Improvements**
  +- Icon: add two new icon [\#396](https://github.com/youzan/vant/pull/396) [@chenjiahan](https://github.com/chenjiahan)
  +- Button: adjust default button border color [\#392](https://github.com/youzan/vant/pull/392) [@chenjiahan](https://github.com/chenjiahan)
  +
  +**Bug Fixes**
  +- Tab: hide scrollbar in mobile safari [\#390](https://github.com/youzan/vant/pull/390) [@chenjiahan](https://github.com/chenjiahan)
  +- Tab: active tab should keep center when scrollable [\#394](https://github.com/youzan/vant/pull/394) [@chenjiahan](https://github.com/chenjiahan)
  +
  ### [0.11.7](https://github.com/youzan/vant/tree/v0.11.7)
  `2017-12-07`
  