require version 2.3+ of symfony/options-resolver & symfony/yaml to support symfony2 lts 2.3 (#1)

in composer.json you require symfony 2.4+ packages. do you really need the 2.4+ versions of:

symfony/options-resolver
symfony/yaml

there do not seem to be mayor updates, which prevent to rely on version 2.3+ of the listed packages.

by relying on 2.3+ you are able to use you package in symfony 2.3 environment. symfony 2.3 is the first long term release. thus it would be great to support it. :)