normalize syntax (#2678)

packages/menu/src/menu-item-group.vue

+<template>
+  <li class="el-menu-item-group">
+    <div class="el-menu-item-group__title" :style="{paddingLeft: levelPadding + 'px'}">
+      <template v-if="!$slots.title">{{title}}</template>
+      <slot v-else name="title"></slot>
+    </div>
+    <ul>
+      <slot></slot>
+    </ul>
+  </li>
+</template>
 <script>
-  module.exports = {
+  export default {
     name: 'ElMenuItemGroup',
 
     componentName: 'ElMenuItemGroup',
@@ -31,14 +42,3 @@
   };
 </script>
 
-<template>
-  <li class="el-menu-item-group">
-    <div class="el-menu-item-group__title" :style="{paddingLeft: levelPadding + 'px'}">
-      <template v-if="!$slots.title">{{title}}</template>
-      <slot v-else name="title"></slot>
-    </div>
-    <ul>
-      <slot></slot>
-    </ul>
-  </li>
-</template>

packages/menu/src/menu-item.vue

@@ -13,7 +13,7 @@
   import Menu from './menu-mixin';
   import Emitter from 'element-ui/src/mixins/emitter';
 
-  module.exports = {
+  export default {
     name: 'ElMenuItem',
 
     componentName: 'ElMenuItem',

packages/menu/src/menu-mixin.js

-module.exports = {
+export default {
   computed: {
     indexPath() {
       var path = [this.index];

packages/menu/src/submenu.vue

@@ -30,7 +30,7 @@
   import Emitter from 'element-ui/src/mixins/emitter';
   import CollapseTransition from 'element-ui/src/transitions/collapse-transition';
 
-  module.exports = {
+  export default {
     name: 'ElSubmenu',
 
     componentName: 'ElSubmenu',

packages/tabs/src/tab-pane.vue

@@ -4,7 +4,7 @@
   </div>
 </template>
 <script>
-  module.exports = {
+  export default {
     name: 'ElTabPane',
 
     componentName: 'ElTabPane',

packages/tabs/src/tabs.vue

 <script>
   import TabNav from './tab-nav';
 
-  module.exports = {
+  export default {
     name: 'ElTabs',
 
     components: {