fix tbody & keying warnings

src/components/views/settings/Notifications.js

@@ -692,17 +692,21 @@ module.exports = React.createClass({
             // and this wouldn't be hard to add.
             var rows = [];
             for (var i = 0; i < this.state.pushers.length; ++i) {
-                rows.push(<tr>
+                rows.push(<tr key={ i }>
                     <td>{this.state.pushers[i].app_display_name}</td>
                     <td>{this.state.pushers[i].device_display_name}</td>
                 </tr>);
             }
             devicesSection = (<table className="mx_UserSettings_devicesTable">
+                <thead>
                     <tr>
                         <th>Application</th>
                         <th>Device</th>
                     </tr>
+                </thead>
+                <tbody>
                     {rows}
+                </tbody>
             </table>);
         }