Test all routes for unavailable data

[vgeorge]

The interface should display a proper error message when a country or model is not available.

[vgeorge]

To clarify, what we need here is that the application to show the "Not found" page when the user access an unavailable country/models. For example:

• http://localhost:9000/explore/mw-20
• http://localhost:9000/countries/aa/models