Remove node_modules folder

The `node_modules` folder was included in the prototyping app to enable quick start without the user (who is often non-technical) having to get involved in dependency management tools.

This is not a requirement for this project so moving `node_modules` out the repository makes sense.

There are some effects on how the app runs on Heroku. Prior to executing the command in `/Procfile`, Heroku runs:

```
npm install --production
```

This will have failed but because the modules were in the repository, this did not matter.
For these proposed changes, I've changed `package.json` so all modules are available in production. This set up has been tested and proven to work when a fresh checkout is followed by:

```
npm install --production
foreman start
```