Update warning when React is not detected

Author: zetachang

lib/hyper-react.rb

@@ -8,7 +8,7 @@
       "A global `React` must be defined before requiring 'hyper-react'",
       "",
       "To USE THE BUILT-IN SOURCE: ",
-      "   add 'require \"react/react-source\"' immediately before the 'require \"hyper-react\" directive.",
+      "   add 'require \"react/react-source-browser\"' immediately before the 'require \"hyper-react\" directive.",
       "IF USING WEBPACK:",
       "   add 'react' to your webpack manifest."
     ].join("\n")