fix(package): update debug to version 4.0.0

Closes #424

Author: greenkeeper[bot]

package.json

@@ -30,7 +30,7 @@
     "async": "2.6.0",
     "body-parser": "1.18.2",
     "cookie-parser": "1.4.3",
-    "debug": "3.1.0",
+    "debug": "4.0.0",
     "express": "4.16.2",
     "express-graphql": "0.6.11",
     "graphql": "0.11.7",