Current master code is not compatible with current Heroku defaults

[mikewadsten]

See #8 for an example of the problems that exist.

TODO list:

• [ ] Add runtime.txt file so that the app can be forced to Python 2.7. (Heroku uses Python 3.6 by default now.)
• [ ] Update package.json to add the prod directory to cacheDirectories.
• [ ] Ensure static front-end assets are "collected" for use by Django (see my comment here) ?!?!

There may be more steps, or changes to the above steps, as we find out more.