Place roast and bay leaves in a large slow cooker. In a food processor or blender, combine vinegar, lime juice, peppers, garlic and seasonings. Process on high until smooth. Pour vinegar mixture and broth over roast. Cover and cook on low setting for 6 to 8 hours, until roast is fork-tender. Shred beef with 2 forks; return to juices in slow cooker. Serve on tortillas with desired toppings.