Fix CostsDelete method (#62)

* change phpunit call to prevent of using global configuration
* fix CostsDelete method

.travis.yml

@@ -16,4 +16,4 @@ before_script:
     - flags="-o"
     - composer install $flags
 
-script: phpunit
+script: php ./vendor/phpunit/phpunit/phpunit -c phpunit.xml.dist

lib/RetailCrm/Methods/V5/Costs.php

@@ -111,7 +111,8 @@ trait Costs
         /* @noinspection PhpUndefinedMethodInspection */
         return $this->client->makeRequest(
             '/costs/delete',
-            "POST"
+            "POST",
+            ['ids' => json_encode($ids)]
         );
     }