Correctly working PHPSpec version is not included by phpunit, no need for us to require it anymore

Author: WyriHaximus

composer.json

@@ -13,7 +13,6 @@
     "jakub-onderka/php-console-highlighter": "^0.3.2",
     "jakub-onderka/php-parallel-lint": "^0.9.2",
     "phake/phake": "^2.3",
-    "phpspec/prophecy": "^1.6",
     "phpunit/phpunit": "^6.0",
     "squizlabs/php_codesniffer": "^2.6"
   },