add remove function to cache

Author: 5im-0n

lib/utils.js

@@ -158,6 +158,9 @@ exports.cache = {
   get: function (key) {
     return this._data[key];
   },
+  remove: function (key) {
+    delete this._data[key];
+  },
   reset: function () {
     this._data = {};
   }