Ошибка при использовании composer для установки Bogardo / Mailgun и php-http / guzzle6-adapter

Question

Я пытаюсь установить пакет mailgun laravel под названием Bogardo / Mailgun вместе с php-http / guzzle6-adapter.

У меня не было проблем при использовании для установки первого пакета с помощью следующей команды:

composer require bogardo/mailgun

Однако, когда я использую:

composer require php-http/guzzle6-adapter

, я получаю следующую ошибку композитора:

C:\xampp\htdocs\dtcburger.com>composer require php-http/guzzle6-adapter
Using version ^2.0 for php-http/guzzle6-adapter
./composer.json has been updated
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
    - nexmo/client 1.7.0 requires php-http/guzzle6-adapter ^1.0 -> satisfiable by php-http/guzzle6-adapter[v1.0.0, v1.1.0, v1.1.1] but these conflict with your requirements or minimum-stability.
    - nexmo/client 1.7.0 requires php-http/guzzle6-adapter ^1.0 -> satisfiable by php-http/guzzle6-adapter[v1.0.0, v1.1.0, v1.1.1] but these conflict with your requirements or minimum-stability.
    - nexmo/client 1.7.0 requires php-http/guzzle6-adapter ^1.0 -> satisfiable by php-http/guzzle6-adapter[v1.0.0, v1.1.0, v1.1.1] but these conflict with your requirements or minimum-stability.
    - Installation request for nexmo/client (locked at 1.7.0) -> satisfiable by nexmo/client[1.7.0].


Installation failed, reverting ./composer.json to its original content.

Я выполняю следующие шаги: https://github.com/Bogardo/Mailgun

Есть идеи, как мне это исправить?

Так выглядит мой файл composer.json:

{
    "name": "laravel/laravel",
    "description": "The Laravel Framework.",
    "keywords": ["framework", "laravel"],
    "license": "MIT",
    "type": "project",
    "require": {
        "php": "^7.1.3",
        "bogardo/mailgun": "^5.0",
        "fideloper/proxy": "^4.0",
        "intervention/image": "^2.4",
        "laravel/framework": "5.7.*",
        "laravel/tinker": "^1.0"
    },
    "require-dev": {
        "beyondcode/laravel-dump-server": "^1.0",
        "filp/whoops": "^2.0",
        "fzaninotto/faker": "^1.4",
        "mockery/mockery": "^1.0",
        "nunomaduro/collision": "^2.0",
        "phpunit/phpunit": "^7.0",
        "stripe/stripe-php": "^6.29"
    },
    "autoload": {
        "classmap": [
            "database/seeds",
            "database/factories"
        ],
        "psr-4": {
            "App\\": "app/"
        },
        "files": ["App/Helpers/Strings.php"]
    },
    "autoload-dev": {
        "psr-4": {
            "Tests\\": "tests/"
        }
    },
    "extra": {
        "laravel": {
            "dont-discover": [
            ]
        }
    },
    "scripts": {
        "post-root-package-install": [
            "@php -r \"file_exists('.env') || copy('.env.example', '.env');\""
        ],
        "post-create-project-cmd": [
            "@php artisan key:generate --ansi"
        ],
        "post-autoload-dump": [
            "Illuminate\\Foundation\\ComposerScripts::postAutoloadDump",
            "@php artisan package:discover --ansi"
        ]
    },
    "config": {
        "preferred-install": "dist",
        "sort-packages": true,
        "optimize-autoloader": true
    },
    "minimum-stability": "dev",
    "prefer-stable": true
}