add possibility to install with codeception 4 (fixes #50, via #53)

Author: vromants

composer.json

@@ -17,7 +17,7 @@
     },
     "require": {
 	    "php": ">=5.6",
-        "codeception/codeception": "^2.3|^3.0",
+        "codeception/codeception": "^2.3|^3.0|^4.0",
         "allure-framework/allure-php-api": "~1.1.7",
         "symfony/filesystem": ">=2.6",
         "symfony/finder": ">=2.6"