Do not require a logger to be present for EventListener\ViewResponseListener
Add alternate dependency on sensio/framework-extra-bundle ~2.3

sensio/framework-extra-bundle ~3.0 requires symfony/symfony ~2.4, but this
bundle must support symfony/symfony ~2.3, which is supported by
sensio/framework-extra-bundle ~2.3
Both versions of framework-extra-bundle are tested by travisci