#99 wip set headers
Merge branch 'develop' of git://github.com/sulu-cmf/SuluMediaBundle into feature/cache-headers
write cache files
fix #99 set cache headers
activate format cache
delete unused datetime
use correct datetime class
add tests
add test
Merge branch 'develop' of git://github.com/sulu-cmf/SuluMediaBundle into feature/cache-headers
add response header test
Merge branch 'develop' of git://github.com/sulu-cmf/SuluMediaBundle into feature/cache-headers
Merge pull request #100 from sulu-cmf/feature/cache-headers

[Feature] cache headers for images
cleanup
fix merge conflict use Symfony Filesystem to delete files