add sebastianbergman/comparator 2.0 to require

Author: ek9

composer.json

@@ -27,6 +27,7 @@
     "require": {
         "php": ">=5.6",
         "phpunit/php-code-coverage": "~4.0||~5.0",
+        "sebastian/comparator": "~2.0",
         "behat/behat": "~3.0",
         "guzzlehttp/guzzle": "~6.0",
         "symfony/config": "~2.3||~3.0||~4.0",
@@ -37,7 +38,6 @@
     },
     "require-dev": {
         "phpunit/phpunit": "~5.0",
-        "sebastian/comparator": "~2.0",
         "mikey179/vfsStream": "1.6.*"
     },
     "suggest": {