[RFR] 2.0.0

 - [x] Update composer.json to use `marmelab/phpcr-api` 2.0.0
 - [x] Update provider to work with the new version
 - [x] Split provider to use `jms/serializer`
 - [x] Add tests for RepositoryController
 - [x] Add tests for WorkspaceController
 - [x] Add tests for NodeController
 - [x] Add tests for NodeHandler
 - [x] Add tests for RepositoryHandler
 - [x] Add tests for PathConverter