Added declare(strict_types=1); (#691)

* Added declare(strict_types=1);

* cs

Author: Nyholm

Tests/Provider/AbstractHttpProviderTest.php

@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Geocoder package.
  * For the full copyright and license information, please view the LICENSE