Optimize React for production

[blgm]

• sets process.env.NODE_ENV = 'production' using envify
• eliminates the (now dead) React development code with uglifyify
• reduces the bundle size from 1028132 bytes to 655814 (36%)
• based on guidance on how to use React with browserify: https://reactjs.org/docs/optimizing-performance.html#browserify
• fixes https://github.com/alanshaw/david-www/issues/390

What I don't like about these changes:

• there is now some minification in a build phase (it should all be in the minify phase)
• you have to change package.json to get a development build (if we knew that NODE_ENV was always set to production on the production server, then we could allow envify to pick it up from the environment, allowing development machines to have a development version of React)
• I haven't updated package-lock.json as both .travis.yml and package.json suggest this is a node 6 project, which does not support package-lock.json by default

I'm happy to try and resolve these with some guidance as to what is preferred.

Testing:

• unit tests pass locally and on Travis
• can run server on my local system
• I was able to reproduce the issue, and show that these changes fixed it

[alanshaw]

The infrastructure project is here, I need to upgrade it to add letsencrypt support this week so I can also do the work to ensure NODE_ENV set to production in the same pass so lets leave it out of the package.json.

I'd appreciate it if you did also submit an updated package-lock.json I want to use a more recent Node.js in production so we'll need it, and it is in the repo now so we should at least keep it up to date.

[alanshaw]

Also, thanks ✨ @blgm ✨

[blgm]

@alanshaw, I've pushed some more changes which hopefully address your comments.