el-menu routing implementation

el-menu 实现路由需要添加 router  :default-active="$route.path"
index="/bar"
<el-menu
        default-active="2"
        class="el-menu-vertical-demo"
        @open="handleOpen"
        :collapse="isCollapse"
        router
        :default-active="$route.path"
        @close="handleClose">
    <el-submenu index="1">
        <template slot="title">
            <i class="el-icon-location"></i>
            <span>工具</span>
        </template>
        <el-menu-item-group>
            <el-menu-item index="/bar"> Mobile </ el-menu-item> 
            <el-menu-item index = "/ foo"> select </ el-menu-item>
            <el-menu-item index="/main">魔法</el-menu-item>
        </el-menu-item-group>

</el-submenu>

</el-menu>

<the-menu