Add clear Limitations section

Author: gaearon

README.md

@@ -91,6 +91,19 @@ Currently it is a thin layer on top of many amazing community projects, such as:
 
 All of them are transient dependencies of the provided npm package.
 
+## Limitations
+
+Some features are currently **not supported**:
+
+* Server rendering
+* Testing
+* Some experimental syntax extensions (e.g. decorators)
+* CSS Modules
+* LESS or Sass
+* Hot reloading of components
+
+Some of them might get added in the future if they are stable, are useful to majority of React apps, don’t conflict with existing tools, and don’t introduce additional configuration.
+
 ## Contributing
 
 Clone the repo and run `npm install` in the root and the `global-cli` folder.