Back Button functionality

The browser back button should work throughout the application as it would in a non-single page app. Data should be populated when you go back through the browser, and the scroll position of the page you go back to should be as it was before you left.

@seankwilliams to provide a more comprehensive set of requirements once the app is more built out.

A starting point for research on how to do this with React Router:
- https://stackoverflow.com/questions/44121069/how-to-pass-params-with-history-push-in-react-router-v4
- Any solution will probably be based in the browser's history API. It may turn out the history API interactions are done by React Router, though.