Add link to active CSS modules discussion (facebook#3163)

* Add link to active CSS modules discussion

* Update README.md

README.md

@@ -191,7 +191,7 @@ Some features are currently **not supported**:
 
 * Server rendering.
 * Some experimental syntax extensions (e.g. decorators).
-* CSS Modules.
+* CSS Modules (see [#2285](https://github.com/facebookincubator/create-react-app/pull/2285)).
 * Importing LESS or Sass directly ([but you still can use them](https://github.com/facebookincubator/create-react-app/blob/master/packages/react-scripts/template/README.md#adding-a-css-preprocessor-sass-less-etc)).
 * Hot reloading of components.