title: Use object :title in URL routes rather than :id
body: <p><em><strong>Update:</strong> please see my answer below for final solution</em></p>
  
  <p>I have an object with unique title names and I'd like to utilise the titles rather than the ID's throughout the website in routes.</p>
  
  <p><strong>routes.js</strong></p>
  
  <pre><code>// Current routing
  
  var articles = require('../app/controllers/articles')
  
  app.param('articleId', articles.load)
  app.get('/articles', articles.index)
  app.get('/articles/new', articles.new)
  app.post('/articles', articles.create)
  app.get('/articles/:articleId', articles.show)
  app.get('/articles/:articleId/edit', articles.edit)
  app.put('/articles/:articleId', articles.update)
  app.del('/articles/:articleId', articles.destroy)
  
  ***
  
  // Desired routing
  
  app.param('articleTitle', articles.load)
  app.get('/articles', articles.index)
  app.get('/articles/new', articles.new)
  app.post('/articles', articles.create)
  app.get('/articles/:articleTitle', articles.show)
  app.get('/articles/:articleTitle/edit', articles.edit)
  app.put('/articles/:articleTitle', articles.update)
  app.del('/articles/:articleTitle', articles.destroy)
  </code></pre>
  
  <p><strong>articles.js (Controller)</strong></p>
  
  <pre><code>exports.load = function(req, res, next, title){
    Article.load(title, function (err, article) {
      if (err) return next(err)
      if (!article) return next(new Error('not found'))
      req.article = article
      next()
    })
  }
  
  exports.show = function(req, res){
    res.render('articles/show', {
      title: req.article.title,
      article: req.article
    })
  }
  </code></pre>
  
  <p><strong>article.js (Model)</strong></p>
  
  <pre><code>ArticleSchema.statics = {
    load: function (title, cb) {
      this.findOne({ title : title })
        .exec(cb)
    }
  }
  </code></pre>
  
  <p>Basically, I've subbed out any id references and replaced them with title references. For some reason they simply are not working. </p>
  
  <p>An example would be going to a URL <code>http://localhost:3000/articles/test</code> rather than <code>http://localhost:3000/articles/5TheId234</code>, which doesn't work, throwing this error: GET /articles/test 404 148ms</p>
  
  <p>Thanks in advance!</p>