fix #95 can not deepcopy set

Author: huybuidac

jest.config.js

@@ -1,3 +1,6 @@
 module.exports = {
   preset: '@vue/cli-plugin-unit-jest',
+  collectCoverageFrom: [
+    'src/index.js'
+  ]
 };

lib/index.js

@@ -1,6 +1,6 @@
 {
   "name": "vuex-extensions",
-  "version": "1.1.5",
+  "version": "1.2.1",
   "description": "Add Reset and Mixins function to Vuex",
   "main": "lib/index.js",
   "types": "types/index.d.ts",

lib/util.js

@@ -1,4 +1,4 @@
-import { deepCopy } from './util'
+const deepCopy = require('./util')({circles: true})
 
 const createStore = (vuexStoreClass, options = {}) => {
   const mixins = options.mixins || {}