我如何解决“您的要求无法解析为可安装的软件包集”错误？

当我运行composer update时，收到了一些奇怪的输出。

这是我的composer.json文件的样子。

{
    "name": "laravel/laravel",
    "description": "The Laravel Framework.", "keywords": ["framework", "laravel"],
    "license": "MIT",
    "repositories": [{
        "type": "vcs",
        "url": "https://github.com/Zizaco/ardent.git"
    }],
    "require-dev": {
        "phpunit/phpunit": "4.3.*"
    },
    "require": {
        "laravel/framework": "4.2.*", 
        "laravelbook/ardent": "dev-master as 2.4.0", 
        "zizaco/entrust": "dev-master", 
        "sebklaus/profiler": "dev-master", 
        "doctrine/dbal": "dev-master"
    },
    "autoload": {
        "classmap": [
            "app/commands",
            "app/controllers",
            "app/models",
            "app/database/migrations", "app/database/seeds", "app/tests",
            "app/libraries"
        ]
    },
    "scripts": {
        "post-install-cmd": [
            "php artisan clear-compiled", 
            "php artisan optimize"
        ],
        "post-update-cmd": [
            "php artisan clear-compiled", 
            "php artisan optimize"
        ],
        "post-create-project-cmd": [
            "php artisan key:generate"
        ]
    },
    "config": {
        "preferred-install": "dist"
    },
    "minimum-stability": "stable"
}

我该如何修复它？