Laravel 5.1.26 Composer Update Error

Getting Error while updating Composer.json in Laravel 5.1.26, I have added a package tcpdf and also tried using the latest version of tcpdf it also showing error,

[RuntimeException]
Could not load package intervention/image in http://packagist.org: [UnexpectedValueException] Could not parse version constraint 4.x.x: In valid version string "4.x.x"

And also tried composer self-update command but says it throws a message.

[InvalidArgumentException] Command "self-update" is not defined.

Donno how to resolve it, this is my composer file with tcpdf package added.

{
    "name": "laravel/laravel",
    "description": "The Laravel Framework.",
    "keywords": ["framework", "laravel"],
    "license": "MIT",
    "type": "project",
    "require": {
        "php": ">=5.5.9",
        "laravel/framework": "5.1.*",
        "illuminate/html": "5.0.*@dev",
        "laravel/socialite": "^2.0",
        "zizaco/entrust": "dev-laravel-5",
        "spatie/activitylog": "^2.1",
        "felixkiss/uniquewith-validator": "2.*",
        "intervention/image": "^2.3",
        "barryvdh/laravel-dompdf": "^0.6.0",
        "maatwebsite/excel": "^2.0",
        "cviebrock/image-validator": "2.0.*@beta",
        "twilio/sdk": "^4.5",
        "guzzlehttp/guzzle": "^6.1",
        "elibyy/laravel-tcpdf": "0.*"   /* =====> TCPDF  */
    },
    "require-dev": {
        "fzaninotto/faker": "~1.4",
        "mockery/mockery": "0.9.*",
        "phpunit/phpunit": "~4.0",
        "phpspec/phpspec": "~2.1"
    },
    "autoload": {
        "classmap": [
            "database"            
        ],
        "psr-4": {
            "App\\": "app/"
        },
        "files": ["app/Http/helpers.php"]
    },
    "autoload-dev": {
        "classmap": [
            "tests/TestCase.php"
        ]
    },
    "scripts": {
        "post-install-cmd": [
            "php artisan clear-compiled",
            "php artisan optimize"
        ],
        "pre-update-cmd": [
            "php artisan clear-compiled"
        ],
        "post-update-cmd": [
            "php artisan optimize"
        ],
        "post-root-package-install": [
            "php -r \"copy('.env.example', '.env');\""
        ],
        "post-create-project-cmd": [
            "php artisan key:generate"
        ]
    },
    "config": {
        "preferred-install": "dist"
    }
}

Thanks in Advance.

via Chebli Mohamed