Refactor `main.js` so only production uses Require.js
Refactor `main.js` so only production uses Require.js

In development, the in-memory bundle is served by WebpackDevServer
so there is no reason to load the modules again with Require.js.

Thus, use `isProduction` from data-config to determine how to
bootstrap the client-side app.

remarkablemark/react-engine-template,remarkablemark/react-engine-template