📝 Add more instrunctions about antd 3 migration

CHANGELOG.en-US.md

@@ -1111,11 +1111,14 @@ Learn more in the [Ant Design 3.0 announcement post](https://medium.com/ant-desi
 - New [Divider](https://ant.design/components/divider/) component.
 - 30 New [icons](https://ant.design/components/icon/).
 
-### Breaking Changes
+### ⚠️ Read it before migration
 
-> We suggest you upgrade to latest 3.x version directly.
+- We suggest you upgrade to latest 3.x version directly.
+- Some APIs may be deprecated in other 3.x versions which don't described below, please pay attention to warning in browser console and upgrade them.
+- We strongly suggest upgrade react to 16 or newest for better support and performance, which could be conduct via [React 16 upgrading](https://reactjs.org/blog/2017/09/26/react-v16.0.html#upgrading).
+- Then you can migrate to antd@3 by following `Breaking Changes` section.
 
-> Some APIs may be deprecated in other 3.x versions which don't described below, please pay attention to warning in browser console and upgrade them.
+### Breaking Changes
 
 We provide a [migration tool](https://github.com/ant-design/antd-migration-helper) to help you find deprecated usages in your codebase.
 

CHANGELOG.zh-CN.md

@@ -1114,11 +1114,14 @@ timeline: true
 - 新的 [Divider](https://ant.design/components/divider-cn/) 组件。
 - 新增 30 个[图标](https://ant.design/components/icon-cn/)。
 
-### 不兼容改动
+### ⚠️ 升级必读
 
-> 如果你从 2.x 升级到 3.x，建议直接升级到 3.x 的最新版本。
+- 如果你从 2.x 升级到 3.x，建议直接升级到 3.x 的最新版本。
+- 3.x 后续的版本可能已经废弃了一些下面没有提到的改动，请参考控制台的警告提示相应升级。
+- 建议同时升级 React 到 16 或更新版本，以获得更好的性能和更完善的支持，升级方式见 [官方发布文档](https://reactjs.org/blog/2017/09/26/react-v16.0.html#upgrading)。
+- 最后请参照下面的不兼容改动进行升级。
 
-> 3.x 后续的版本可能已经废弃了一些下面没有提到的改动，请参考控制台的警告提示相应升级。
+### 不兼容改动
 
 此版本有部分不兼容的改动，升级时确保修改相应的使用代码。另外由于人肉查找代码中的废弃用法过于低效，所以我们提供了 [antd-migration-helper](https://github.com/ant-design/antd-migration-helper) 用于扫描代码中的废弃用法。