我有一个目录结构

projectName
    | - bower_components/
    | - public/
        | - css
        | - js
        | - index.html
    | - Gruntfile.js
    | - package.json
    | - bower.json
    | - app.js

我想启动我的应用并index.html与节点一起使用。所以app.js我有：

var express = require('express');
var port = process.env.PORT || 3000;
var app = express();

app.configure(function(){
    // Serve up content from public directory
    app.use(express.static(__dirname + '/public'));
    app.use(app.router);
    app.use(express.logger()); 
});

app.listen(port, function(){
    console.log('Express server listening on port ' + port);
});

在index.html我的底部：

<script src="../bower_components/jquery/jquery.js"></script>
<script src="../bower_components/d3/d3.js"></script>
<script src="../bower_components/bootstrap/dist/js/bootstrap.js"></script>
<script src="bower_components/spin.js/spin.js"></script>
<script src="bower_components/mustache/mustache.js"></script>

当我启动服务器时，index.html显示出来，但以上库均未加载。我收到错误消息（404）：

GET http://localhost:3000/bower_components/jquery/jquery.js 404 (Not Found) localhost/:32
GET http://localhost:3000/bower_components/d3/d3.js 404 (Not Found) localhost/:33
GET http://localhost:3000/bower_components/bootstrap/dist/js/bootstrap.js 404 (Not Found) localhost/:34
GET http://localhost:3000/bower_components/spin.js/spin.js 404 (Not Found) localhost/:35
GET http://localhost:3000/bower_components/mustache/mustache.js 404 (Not Found)

如何提供来自bower_components的文件？