Only require the package for dev environments by default.

Given that the API docs are just static files, the generator does not need to be shipped in production environments.

Therefore, this change updates the `composer require` command in the README to only require the package in dev environments.

README.md

@@ -15,7 +15,7 @@ Automatically generate your API documentation from your existing Laravel/Lumen/[
 PHP 7 and Laravel 5.5 or higher are required.
 
 ```sh
-composer require mpociot/laravel-apidoc-generator
+composer require --dev mpociot/laravel-apidoc-generator
 ```
 
 ### Laravel
@@ -28,6 +28,7 @@ php artisan vendor:publish --provider="Mpociot\ApiDoc\ApiDocGeneratorServiceProv
 This will create an `apidoc.php` file in your `config` folder.
 
 ### Lumen
+- When using Lumen, you will need to run `composer require mpociot/laravel-apidoc-generator` instead.
 - Register the service provider in your `bootstrap/app.php`:
 
 ```php