Upgrade monolog dep to 1.5 (was 1.4)
Upgrade zendframework dep to version 2.2.* (was 2.1)
Upgrade symfony/* deps to version 2.3.* (was 2.2)
Replace obsolete FlashBag::count() call with count(FlashBag::peekAll())
Bring back support for Symfony's ContainerInterface
CS fix