Update table name

Closes #15 and CartBundle/issues#1
Closes #12
[RFC] Added method to return the total amount of items in a Cart
[CartBundle] Fixes #19. Remove Cart::isDeleted() occurrences
Fixes #23 [UserBundle] Store new customer id in session
Fixes #25 [CartBundle] Refactor Cart::getNbItems()
Issue #26. Migrating to PSR-4