Verify that npm prune is working, and if not get it working

[jonespm]

It looks like we could maybe optimize how node_modules is built. Some of the dependencies under devDependencies are more like dependencies (@material-ui, js-cookie, typeface-roboto?). Looking at the Docker artifacts, I see there is an effort to remove extraneous packages (npm prune --production), but I'm not sure if it's actually working. When I go to OpenShift and peak inside node_modules, I still see jest, webpack, -loader, etc. We should probably also make sure that the frontend unit test and related artifacts are left behind from the production images (currently, they are under assets/src/__tests__).

Originally posted by @ssciolla in #1363 (comment)

[jonespm]

Also from a comment in that threat

It looks like @justin0022 originally added the npm prune afd74b5.

I've never checked to see if it's working either.

It looks like it might have to be combined with node-prune to really remove the node_modules. I saw that mentioned in this article here: itsopensource.com/how-to-reduce-node-docker-image-size-by-ten-times

I think we can just address this in a separate issue but yeah having the appropriate things in devDependencies makes sense to me.

[jonespm]

This is somewhat related to #987 that hasn't been merged yet