Update debug to 4.0.0

Author: addaleax

package.json

@@ -24,7 +24,7 @@
     "test": "node-gyp rebuild --directory test && nyc mocha -gc --reporter spec"
   },
   "dependencies": {
-    "debug": "^3.1.0"
+    "debug": "^4.0.0"
   },
   "devDependencies": {
     "binding": "^3.0.3",