Symfony Flex

[PouleR]

Make the bundle compatible with Symfony Flex to make it easier to install the bundle in Symfony 4 environments.

http://symfony.com/doc/current/setup/flex.html#upgrading-existing-applications-to-flex

[Martin1982]

Set the milestone to 1.0.1 as Symfony Flex recipes require a separate repository; https://github.com/symfony/recipes-contrib