Remove unused error response class (#319)

src/Mailgun/Model/ErrorResponse.php

@@ -1,61 +0,0 @@
-<?php
-
-/*
- * Copyright (C) 2013-2016 Mailgun
- *
- * This software may be modified and distributed under the terms
- * of the MIT license. See the LICENSE file for details.
- */
-
-namespace Mailgun\Model;
-
-final class ErrorResponse implements ApiResponse
-{
-    /**
-     * @var string
-     */
-    private $message;
-
-    /**
-     * @var string
-     */
-    private $error;
-
-    /**
-     * @param string $error
-     */
-    private function __construct($message, $error)
-    {
-        $this->message = $message;
-        $this->error = $error;
-    }
-
-    /**
-     * @param array
-     *
-     * @return self
-     */
-    public static function create(array $data)
-    {
-        return new self(
-            isset($data['message']) ? $data['message'] : null,
-            isset($data['error']) ? $data['error'] : null
-        );
-    }
-
-    /**
-     * @return string
-     */
-    public function getMessage()
-    {
-        return $this->message;
-    }
-
-    /**
-     * @return string
-     */
-    public function getError()
-    {
-        return $this->error;
-    }
-}