Move travis to xenial
Move travis to xenial

CanalTP/navitia,xlqian/navitia,Tisseo/navitia,pbougue/navitia,xlqian/navitia,pbougue/navitia,xlqian/navitia,xlqian/navitia,kinnou02/navitia,kinnou02/navitia,Tisseo/navitia,kinnou02/navitia,Tisseo/navitia,pbougue/navitia,Tisseo/navitia,CanalTP/navitia,pbougue/navitia,CanalTP/navitia,Tisseo/navitia,CanalTP/navitia,CanalTP/navitia,kinnou02/navitia,xlqian/navitia