Bump version of KnpMenuBundle 1.* -> ^2.1,
It will be possible to use twig/twig in ^2.x version with this change

knplabs/knp-menu-bundle ~1.1 requires knplabs/knp-menu ~1.1, which requires twig/twig >=1.2,<2.0-dev

knplabs/knp-menu-bundle 2.x requires knplabs/knp-menu ~2.1 , which requires twig/twig ~1.16|~2.0