Fix vfsStream requierments

`vfsStream` has set their `dev-master` to >PHP 7.1 so we need to Fall back to release `1.6.5` to remove build errors
reference bovigo/vfsStream#143

composer.json

@@ -17,7 +17,7 @@
 		}
 	],
 	"require-dev": {
-		"mikey179/vfsStream": "dev-master",
+		"mikey179/vfsStream": "1.6.5||dev-master",
 		"phpunit/phpunit": "~4.8||~5.7",
 		"phpunit/dbunit": "~1.4||~2.0",
 		"mockery/mockery": "0.9.4||~0.9.5",