Temp fix to only use react-server

SSR only need react-server, but we still need a copy of ReactDOM in the assets.

Author: zetachang

Diff for: lib/generators/reactive_ruby/test_app/templates/assets/javascripts/components.rb

@@ -1,4 +1,4 @@
 require 'opal'
-require 'react/react-source'
+require 'react-server.js'
 require 'hyper-react'
 require_tree './components'