deps: Update debug to fix security issue

https://nodesecurity.io/advisories/534

Author: danez

package.json

@@ -33,7 +33,7 @@
     "mocha": "~2.0.1"
   },
   "dependencies": {
-    "debug": "~2.2.0",
+    "debug": "~3.1.0",
     "gonzales-pe": "^3.4.4",
     "node-source-walk": "^3.2.0"
   }