As a developer, I want more robust query string parsing & not found checks

[billdybas]

Current implementation for student submitting to a show works if you're only clicking in the app.

If you modify the URL, things start to break. Adding additional query params before to causes links to format incorrectly, and attempting to view the submission forms for a show that doesn't exist causes the app to crash – should be a not found page.

See #187

https://www.npmjs.com/package/query-string might be of use here since react-router no longer parses query strings