I start the tutorial (as newbie) and everythings works fine till:
http://symfony.com/doc/current/book/page_creation.html#creating-a-page-route-and-controller at step
Sometimes is a cache problem. Try to remove dev folder from /project/var/cache/dev.
As authentictech says, also you can try the command:
php bin/console cache:clear
If you want to specify the environment, you should add the --env=prod property.