Update serializer version

[lahaxearnaud]

jms/serializer version is set to ~0.13. It will be great to update to at least 1.0.

[petrepatrasc]

Please this. Using the serializer bundle in combination with ocular only works on 0.13, which makes upgrading to Symfony 3 harder.

[Majkl578]

Dependency is now on ^1.0.0, can be closed. // cc @schmittjoh