作曲家更新包消失错误

我得到了一个由 laravel 克隆项目的新副本，这是作曲家的内部.json

{
    "name": "laravel/laravel",
    "description": "The Laravel Framework.",
    "keywords": ["framework", "laravel"],
    "license": "MIT",
    "require": {
        "laravel/framework": "4.2.*",
        "vtalbot/markdown": "1.*",
        "mews/purifier": "dev-master",
        "hybridauth/hybridauth": "dev-master#6d89473",
        "symfony/yaml": "dev-master",
        "greggilbert/recaptcha": "1.*",
        "php": ">=5.3.0",
        "ext-curl": "*",
        "ext-json": "*",
        "gloudemans/shoppingcart": "~1.2",
        "stripe/stripe-php":"dev-master"
    },
    "autoload": {
        "classmap": [
            "app/commands",
            "app/controllers",
            "app/models",
            "app/database/migrations",
            "app/database/seeds",
            "app/tests/TestCase.php"
        ],
        "files" : [
            "vendor/stripe/stripe-php/lib/Stripe.php"
        ]
    },
    "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"
}

但是当我尝试composer update时，我收到此错误：

$ composer update
Loading composer repositories with package information
Updating dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages.
  Problem 1
    - Conclusion: don't install laravel/framework v4.2.19
    - Conclusion: don't install laravel/framework v4.2.18
    - Conclusion: don't install laravel/framework v4.2.17
    - Conclusion: don't install laravel/framework v4.2.16
    - Conclusion: don't install laravel/framework v4.2.15
    - Conclusion: don't install laravel/framework v4.2.14
    - Conclusion: don't install laravel/framework v4.2.13
    - Conclusion: don't install laravel/framework v4.2.12
    - Conclusion: don't install laravel/framework v4.2.11
    - Conclusion: don't install laravel/framework v4.2.10
    - Conclusion: don't install laravel/framework v4.2.9
    - Conclusion: don't install laravel/framework v4.2.8
    - Conclusion: don't install laravel/framework v4.2.7
    - Conclusion: don't install laravel/framework v4.2.6
    - Conclusion: don't install laravel/framework v4.2.5
    - Conclusion: don't install laravel/framework v4.2.4
    - Conclusion: don't install laravel/framework v4.2.3
    - Installation request for mews/purifier dev-master -> satisfiable by mews/purifier[dev-master].
    - Conclusion: don't install laravel/framework v4.2.2
    - Conclusion: don't install laravel/framework v4.2.1
    - mews/purifier dev-master requires illuminate/filesystem ~5.1 -> satisfiable by illuminate/filesystem[v5.1.1, v5.1.13, v5.1.16, v5.1.2, v5.1.20, v5.1.22, v5.1.25, v5.1.28, v5.1.30, v5.1.31, v5.1.6, v5.1.8, v5.2.0, v5.2.19, v5.2.21, v5.2.6, v5.2.7].
    - don't install illuminate/filesystem v5.1.1|don't install laravel/framework v4.2.0
    - don't install illuminate/filesystem v5.1.13|don't install laravel/framework v4.2.0
    - don't install illuminate/filesystem v5.1.16|don't install laravel/framework v4.2.0
    - don't install illuminate/filesystem v5.1.2|don't install laravel/framework v4.2.0
    - don't install illuminate/filesystem v5.1.20|don't install laravel/framework v4.2.0
    - don't install illuminate/filesystem v5.1.22|don't install laravel/framework v4.2.0
    - don't install illuminate/filesystem v5.1.25|don't install laravel/framework v4.2.0
    - don't install illuminate/filesystem v5.1.28|don't install laravel/framework v4.2.0
    - don't install illuminate/filesystem v5.1.30|don't install laravel/framework v4.2.0
    - don't install illuminate/filesystem v5.1.31|don't install laravel/framework v4.2.0
    - don't install illuminate/filesystem v5.1.6|don't install laravel/framework v4.2.0
    - don't install illuminate/filesystem v5.1.8|don't install laravel/framework v4.2.0
    - don't install illuminate/filesystem v5.2.0|don't install laravel/framework v4.2.0
    - don't install illuminate/filesystem v5.2.19|don't install laravel/framework v4.2.0
    - don't install illuminate/filesystem v5.2.21|don't install laravel/framework v4.2.0
    - don't install illuminate/filesystem v5.2.6|don't install laravel/framework v4.2.0
    - don't install illuminate/filesystem v5.2.7|don't install laravel/framework v4.2.0
    - Installation request for laravel/framework 4.2.* -> satisfiable by laravel/framework[v4.2.0, v4.2.1, v4.2.10, v4.2.11, v4.2.12, v4.2.13, v4.2.14, v4.2.15, v4.2.16, v4.2.17, v4.2.18, v4.2.19, v4.2.2, v4.2.3, v4.2.4, v4.2.5, v4.2.6, v4.2.7, v4.2.8, v4.2.9].

有人对这个错误有所了解吗？