📝 document SSR and HMR incompatibility.

Author: edelgado

README.md

@@ -681,10 +681,12 @@ TheRubyRacer [hasn't updated LibV8](https://github.com/cowboyd/therubyracer/blob
 LibV8 itself is already [beyond version 7](https://github.com/cowboyd/libv8/releases/tag/v7.3.492.27.1) therefore many serverside issues are caused by old JS engines and fixed by using an up to date one such as [MiniRacer](https://github.com/discourse/mini_racer) or [TheRubyRhino](https://github.com/cowboyd/therubyrhino) on JRuby.
 
 ### HMR
-HMR is [possible with this gem](https://stackoverflow.com/a/54846330/193785) as it does just pass through to Webpacker. Please open an issue to let us know tips and tricks for it to add to the wiki.
+Hot Module Replacement is [possible with this gem](https://stackoverflow.com/a/54846330/193785) as it does just pass through to Webpacker. Please open an issue to let us know tips and tricks for it to add to the wiki.
 
 Sample repo that shows HMR working with `react-rails`: [https://github.com/edelgado/react-rails-hmr](https://github.com/edelgado/react-rails-hmr)
 
+One caveat is that currently you [cannot Server-Side Render along with HMR](https://github.com/reactjs/react-rails/issues/925#issuecomment-415469572). 
+
 ## Related Projects
 
 - [webpacker-react](https://github.com/renchap/webpacker-react): Integration of React with Rails utilizing Webpack with Hot Module Replacement (HMR).