Manage trailing slashes with express-slash

This adds express-slash middleware to have canonical URLs with trailing slashes (or not), and redirects to the canonical form.

I also added basic logging to the app in dev (used this to test that express-slash was working correctly).

**Note:** When clicking around the links on the site they are pointing to the non-canonical form of the URLs, causing a redirect to always happen. This is not ideal, and URLs should not be hard coded because this kind of thing happens.