Bump dependencies

Author: theofidry

composer.json

@@ -17,6 +17,8 @@
         }
     ],
 
+    "minimum-stability": "dev",
+    "prefer-stable": true,
     "require": {
         "php": "^7.1",
         "nikic/php-parser": "^4.0",
@@ -28,7 +30,7 @@
     },
     "require-dev": {
         "bamarni/composer-bin-plugin": "^1.1",
-        "humbug/box": "^3.0@rc",
+        "humbug/box": "^3.1",
         "phpunit/phpunit": "^7.0"
     },
     "replace": {