First of all, thank you for your contribution! :-)

Please makes sure that these checkboxes are checked before submitting your pull request, thank you!

* [ ] Make sure that you propose pull request to right branch: bugfix for `master`, feature for branch `feature`.
* [ ] Make sure that you follow antd's [code convention](https://github.com/ant-design/ant-design/wiki/Code-convention-for-antd).
* [ ] Run `npm run lint` and fix those errors before submitting in order to keep consistent code style.
* [ ] Rebase before creating a pull request to keep commit history clear.
* [ ] Add some descriptions and refer relative issues for you pull request.

Extra checklist:

**if** *isBugFix* **:**

  * [ ] Make sure that you add at least one unit test for the bug which you had fixed.

**elif** *isNewFeature* **:**

  * [ ] Update API docs for the component.
  * [ ] Update/Add demo to demonstrate new feature.
  * [ ] Update TypeScript definition for the component.
  * [ ] Add unit tests for the feature.