feat: make `Button` easy to use

components/button/demo/button-group.md

@@ -2,14 +2,15 @@
 
 - order: 5
 
-可以将多个 `Button` 放入 `ButtonGroup` 的容器中。
+可以将多个 `Button` 放入 `Button.Group` 的容器中。
 
 通过设置 `size` 为 `large` `small` 分别把按钮组合设为大、小尺寸。若不设置 `size`，则尺寸为中。
 
 ---
 
 ````jsx
-import { Button, ButtonGroup, Icon } from 'antd';
+import { Button, Icon } from 'antd';
+const ButtonGroup = Button.Group;
 
 ReactDOM.render(<div>
 <h4>基本组合</h4>

components/button/index.jsx

 import Button from './button';
 import ButtonGroup from './button-group';
 
-export {
-  Button,
-  ButtonGroup,
-};
+Button.Group = ButtonGroup;
+export default Button;

components/progress/demo/circle-dynamic.md

@@ -7,8 +7,9 @@
 ---
 
 ````jsx
-import { Progress, Button, ButtonGroup, Icon } from 'antd';
+import { Progress, Button, Icon } from 'antd';
 const ProgressCircle = Progress.Circle;
+const ButtonGroup = Button.Group;
 
 const MyProgress = React.createClass({
   getInitialState() {

components/progress/demo/dynamic.md

@@ -7,8 +7,9 @@
 ---
 
 ````jsx
-import { Progress, Button, ButtonGroup, Icon } from 'antd';
+import { Progress, Button, Icon } from 'antd';
 const ProgressLine = Progress.Line;
+const ButtonGroup = Button.Group;
 
 const MyProgress = React.createClass({
   getInitialState() {

index.js

@@ -48,8 +48,8 @@ const antd = {
   Badge: require('./components/badge'),
   Menu: require('./components/menu'),
   Timeline: require('./components/timeline'),
-  Button: require('./components/button').Button,
-  ButtonGroup: require('./components/button').ButtonGroup,
+  Button: require('./components/button'),
+  ButtonGroup: require('./components/button').Group,
   Icon: require('./components/iconfont'),
   Row: require('./components/layout').Row,
   Col: require('./components/layout').Col,