Fix unorderd tour list bug.
Add search box to manage tour page
Limit customers table to 200px.
Fix bug in TourMapper#update.

Calling #update several times in a row caused the customers for one tour to be duplicated because the join table was never cleaned up.
Return date and tour name from ListStations interactor.
Add Tour#show page.
Move summary calculation to tours controller.
Rename "Dashboard" to "Startseite".
Fix specs.
CreateInvoice interactor; Invoice and LineItem models.
Remove link to invoices from dashboard.
Filter invoices by customer.

Improve invoices view.
Add month pagination to invoices.
Merge pull request #121 from nubedianGmbH/create-invoice

Invoice creation should happen only monthly.
Show customers on new orders page by surname.
Eager load addresses when querying customers.
Eager load keys for addresses.
Eager load catchment areas for customers.
Fix specs.
Add customer importer.