title: class not found with composer autoloader
body: <p>I have this in my <code>composer.json</code></p>
  
  <pre><code>{
      "name": "laravel/laravel",
      "description": "The Laravel Framework.",
      "keywords": ["framework", "laravel"],
      "license": "MIT",
      "type": "project",
      "require": {
          "php": "&gt;=7.0.0",
          "alchemy/zippy": "^0.4.8",
          "barryvdh/laravel-debugbar": "^3.1",
          "fideloper/proxy": "~3.3",
          "graham-campbell/exceptions": "^10.0",
          "intervention/image": "^2.4",
          "intervention/imagecache": "^2.3",
          "laravel/framework": "5.5.*",
          "laravel/tinker": "~1.0",
          "laravelcollective/html": "^5.5",
          "symfony/dom-crawler": "^3.3"
      },
      "files": [
          "vendor/redbutton/text-image-alpha/vendor/autoload.php"
      ],
      "require-dev": {
          "filp/whoops": "^2.1",
          "fzaninotto/faker": "~1.4",
          "mockery/mockery": "0.9.*",
          "phpunit/phpunit": "~6.0"
      },
      "autoload": {
          "classmap": [
              "database/seeds",
              "database/factories"
          ],
          "psr-4": {
              "App\\": "app/"
          }
      },
      "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"
          ],
          "post-autoload-dump": [
              "Illuminate\\Foundation\\ComposerScripts::postAutoloadDump",
              "@php artisan package:discover"
          ]
      },
      "config": {
          "preferred-install": "dist",
          "sort-packages": true,
          "optimize-autoloader": true
      }
  }
  </code></pre>
  
  <p>The php files for my package are in a laravel installation:
  <code>/vendor/redbutton/text-image-alpha/src/</code></p>
  
  <p>When I try to call a file I get the message:</p>
  
  <pre><code>Class 'Class 'RedButton\TextImageAlpha\TextImageAlpha' not found' not found
  </code></pre>
  
  <p>I use this to try and call the class:</p>
  
  <pre><code>$image     = new \RedButton\TextImageAlpha\TextImageAlpha( 'some string' );
  </code></pre>
  
  <p>The file in <code>/vendor/redbutton/text-image-alpha/src/TextImageAlpha.php</code> looks like this:</p>
  
  <pre><code>&lt;?php
  namespace RedButton\TextImageAlpha;
  
  use RedButton\TextImageAlpha\Exceptions;
  use RedButton\Tools\Objects;
  
  
  /**
   * TextImageAlpha class convert a text to image.
   *
   * @author Tomas Rathouz &lt;trathouz at gmail.com&gt;
   */
  class TextImageAlpha
  {
     // lots of code
  }
  </code></pre>
  
  <p>This is my first composer package and I don't really have an idea of what is going wrong here. Could someone please explain to me what I'm doing wrong?</p>