return promise object from fetch

components/table/demo/ajax.md

@@ -65,7 +65,9 @@ var dataSource = new Table.DataSource({
 });
 
 function fetch() {
-  dataSource.fetch();
+  dataSource.fetch().then(function() {
+    console.log('fetch done');
+  });
 }
 
 React.render(<div>

components/table/index.jsx

@@ -349,7 +349,7 @@ var AntTable = React.createClass({
       }
       // remote 模式使用 this.dataSource
       let dataSource = this.getRemoteDataSource();
-      jQuery.ajax({
+      return jQuery.ajax({
         url: dataSource.url,
         data: dataSource.getParams.apply(this, this.prepareParamsArguments(state)) || {},
         headers: dataSource.headers,