feature: add a redirect url when not logged in

https://github.com/PanJiaChen/vue-element-admin/issues/438

src/permission.js

@@ -30,7 +30,7 @@ router.beforeEach((to, from, next) => {
     if (whiteList.indexOf(to.path) !== -1) {
       next()
     } else {
-      next('/login')
+      next(`/login?redirect=${to.path}`) // 否则全部重定向到登录页
       NProgress.done()
     }
   }