Moved phpunit to require-dev

Author: LasseRafn

composer.json

@@ -17,7 +17,9 @@
 	"require": {
 		"php": "^7.0|^7.1",
 		"intervention/image": "^2.3",
-		"intervention/imagecache": "^2.3",
+		"intervention/imagecache": "^2.3"
+	},
+	"require-dev": {
 		"phpunit/phpunit": "^5.7"
 	},
 	"autoload": {