Add migration instructions

CHANGELOG.md

@@ -11,6 +11,13 @@
 * The `otf` font format is now supported. ([@A-gambit](https://github.com/A-gambit) in [#434](https://github.com/facebookincubator/create-react-app/pull/434))
 * The `new-cap` linting rule has been disabled thanks to feedback from Immutable.js users. ([@rricard](https://github.com/rricard) in [#470](https://github.com/facebookincubator/create-react-app/pull/470))
 
+### Migrating from 0.2.1 to 0.2.2
+
+Update `react-scripts` to point to `0.2.2` in your `package.json` and run `npm install`. You shouldn’t need to do anything else.
+
+Newly created projects will use `0.2.2` automatically. You **don’t** need to update the global `create-react-app` CLI itself. It stays at `0.2.0` for now because it doesn’t have any changes.
+
+
 ## 0.2.1 (August 1, 2016)
 
 ### Build Dependency (`react-scripts`)