Expect a PSR-18 client instead of a PHP-HTTP client (#1110)

* Expect a PSR-18 client instead of a PHP-HTTP client

* Update integration tests

Author: JaZo

Tests/IntegrationTest.php

@@ -14,7 +14,7 @@
 
 use Geocoder\IntegrationTest\ProviderIntegrationTest;
 use Geocoder\Provider\HostIp\HostIp;
-use Http\Client\HttpClient;
+use Psr\Http\Client\ClientInterface;
 
 /**
  * @author Tobias Nyholm <[email protected]>
@@ -31,7 +31,7 @@ class IntegrationTest extends ProviderIntegrationTest
 
     protected $testIpv6 = false;
 
-    protected function createProvider(HttpClient $httpClient)
+    protected function createProvider(ClientInterface $httpClient)
     {
         return new HostIp($httpClient);
     }