I think we should use:

    $ composer require sensio/generator-bundle:2.2.* symfony-cmf/blog-bundle:dev-auto_route

Or:

    $ composer require sensio/generator-bundle "2.2.*" --no-update
    $ composer require symfony-cmf/blog-bundle "dev-auto_route" --no-update
    $ composer update sensio/generator-bundle symfony-cmf/blog-bundle