Update package.json

A security vulnerability affecting JWT-SIMPLE package. 

 Patched in    │ >=0.5.3       

firebase-server > jwt-simple  

 https://npmjs.com/advisories/831

Author: loayg

package.json

@@ -60,7 +60,7 @@
     "daemon": "^1.1.0",
     "debug": "^3.1.0",
     "firebase": ">= 5.0.0",
-    "jwt-simple": "0.3.1",
+    "jwt-simple": "0.5.6",
     "lodash": "^4.17.5",
     "targaryen": "3.0.1",
     "ws": "^5.0.0"