Add badge demo

components/badge/demo/change.md

@@ -0,0 +1,52 @@
+# 动态
+
+- order: 4
+
+展示动态变化的效果。
+
+---
+
+````jsx
+import { Badge, Button, Icon } from 'antd';
+const ButtonGroup = Button.Group;
+
+const Test = React.createClass({
+  getInitialState() {
+    return {
+      count: 5
+    };
+  },
+  increase() {
+    const count = this.state.count + 1;
+    this.setState({ count });
+  },
+  decline() {
+    let count = this.state.count - 1;
+    if (count < 0) {
+      count = 0;
+    }
+    this.setState({ count });
+  },
+  render() {
+    return <div>
+      <Badge count={this.state.count}>
+        <a href="#" className="head-example"></a>
+      </Badge>
+      <div style={{ marginTop: 10 }}>
+        <ButtonGroup>
+          <Button type="ghost" onClick={this.decline}>
+            <Icon type="minus" />
+          </Button>
+          <Button type="ghost" onClick={this.increase}>
+            <Icon type="plus" />
+          </Button>
+        </ButtonGroup>
+      </div>
+    </div>;
+  }
+});
+
+ReactDOM.render(
+  <Test />
+, document.getElementById('components-badge-demo-change'));
+````