chore(package): update vfile to version 4.1.0

Closes #109

Author: greenkeeper[bot]

package.json

@@ -41,7 +41,7 @@
     "rimraf": "2.6.2",
     "snazzy": "8.0.0",
     "standard": "12.0.1",
-    "vfile": "2.3.0",
+    "vfile": "4.1.0",
     "weallbehave": "1.2.0"
   }
 }