add layout component with header, content, sider and footer

src/components/layout/layout.vue

@@ -0,0 +1,43 @@
+<template>
+     <div :class="wrapClasses"><slot></slot></div>
+ </template>
+ <script>
+     const prefixCls = 'ivu-layout';
+ 
+     export default {
+         name: 'Layout',
+         props: {
+             className: {
+                 type: String,
+                 default: ''
+             }
+         },
+         data () {
+             return {
+                 prefixCls: prefixCls,
+                 hasSider: false
+             };
+         },
+         computed: {
+             wrapClasses () {
+                 return [
+                     `${prefixCls}`,
+                     this.className,
+                     {
+                         [`${prefixCls}-has-sider`]: this.hasSider
+                     }
+                 ];
+             }
+         },
+         methods: {
+             findSider () {
+                 return this.$children.some(child => {
+                     return child.$options._componentTag === 'Sider';
+                 });
+             }
+         },
+         mounted () {
+             this.hasSider = this.findSider();
+         }
+     };
+ </script>