display 404 page: invalid route / record not found

- rescue_from ActionController::RoutingError doesn’t do anything
- `unless Rails.env.production?` made record not found work
- added tests! :-)
- new errors controller
- handle 422 & 500 errors with public pages
- annotate routes
Merge pull request #249 from codebender/fix/custom_404_page

Display custom 404 page: invalid route / record not found - Bounty #428