fix(package): update pify to version 4.0.0

Author: greenkeeper[bot]

package.json

@@ -35,7 +35,7 @@
     "ghauth": "^3.2.1",
     "meow": "^3.7.0",
     "octokat": "^0.9.2",
-    "pify": "^3.0.0",
+    "pify": "^4.0.0",
     "stringorarraytoarray": "^1.0.1"
   },
   "devDependencies": {