Add documentation

Author: mnapoli

README.md

@@ -5,5 +5,57 @@
 ## Installation
 
 ```
-$ composer require php-di/slim-bridge
+composer require php-di/slim-bridge
+```
+
+## Usage
+
+Instead of using `Slim\App`, simply use `DI\Bridge\Slim\App`:
+
+```php
+<?php
+require 'vendor/autoload.php';
+
+$app = new \DI\Bridge\Slim\App;
+```
+
+You can then use the application [just like a classic Slim application](http://www.slimframework.com/):
+
+```php
+use Psr\Http\Message\ServerRequestInterface as Request;
+use Psr\Http\Message\ResponseInterface as Response;
+
+$app->get('/hello/{name}', function (Request $request, Response $response) {
+    $response->getBody()->write("Hello!");
+    return $response;
+});
+
+$app->run();
+```
+
+### Configuring PHP-DI
+
+If you want to configure PHP-DI, simply extend the `DI\Bridge\Slim\App` class and override the `configureContainer()` method:
+
+```php
+class MyApp extends \DI\Bridge\Slim\App
+{
+    protected function configureContainer(ContainerBuilder $builder)
+    {
+        $builder->addDefinitions(__DIR__ . 'my-config-file.php');
+    }
+}
+
+$app = new MyApp;
+```
+
+Or if you are using PHP 7 you can use anonymous classes:
+
+```php
+$app = new class() extends \DI\Bridge\Slim\App {
+   protected function configureContainer(ContainerBuilder $builder)
+   {
+       $builder->addDefinitions(__DIR__ . 'my-config-file.php');
+   }
+};
 ```