Update the React.js demo and migrate it to a build-free setup.

[bryanbraun]

This will include the following updates:

• To simplify the codebase, we'd like to make this demo build-free, by using an in-browser babel download, as described here.
  • Once this is done, we can remove the task from package.json that was triggering this build.
  • At this point, we can can also remove /examples/react/script-compiled.js
• We want to the latest version of each of the dependencies, and place them in the examples/react folder.
  • Please commit the actual dependency files to the codebase instead of using CDN links.
  • Minified files are preferred, but non-minified works.
  • The filename should include the version number in it (for example: jquery-3.0.0.min.js).
• Update the demo to use the new setup, including any necessary code changes to the demo.
• Verify that the demo works across a sample of modern browsers (like Firefox, Chrome, Safari, and Edge).
  • Follow the instructions here to run a test version of the site locally.
• Commit your changes and submit a pull request.