Improve documentation

Author: SimonFrings

.gitignore

@@ -1,2 +1,2 @@
-/vendor
 /composer.lock
+/vendor/

README.md

@@ -58,6 +58,10 @@ Once [installed](#install), you can use the following code to access the
 Docker API of your local docker daemon:
 
 ```php
+<?php
+
+require __DIR__ . '/vendor/autoload.php';
+
 $client = new Clue\React\Docker\Client();
 
 $client->imageSearch('clue')->then(function (array $images) {
@@ -379,7 +383,7 @@ See also the [CHANGELOG](CHANGELOG.md) for details about version upgrades.
 
 This project aims to run on any platform and thus does not require any PHP
 extensions and supports running on legacy PHP 5.3 through current PHP 8+.
-It's *highly recommended to use PHP 7+* for this project.
+It's highly recommended to use the latest supported PHP version for this project.
 
 ## Tests
 
@@ -393,7 +397,7 @@ $ composer install
 To run the test suite, go to the project root and run:
 
 ```bash
-$ php vendor/bin/phpunit
+$ vendor/bin/phpunit
 ```
 
 ## License