title: Sequelize underscore / snake case when converted to json
body: <p>Using Node and Sequelize, is it possible to define a model which uses camelCase for the attributes, but underscore/snake case when converted to json?</p>
  
  <p>Currently;</p>
  
  <pre><code>var User = seq.define('user', {
      id: {
          type: Sequelize.INTEGER,
          primaryKey: true
      },
      shortLivedToken: {
          type: Sequelize.STRING,
          field: 'short_lived_token'
      },
      longLivedToken: {
          type: Sequelize.STRING,
          field: 'long_lived_token'
      }
  }, {
      underscored: true,
      underscoredAll: true,
  });
  </code></pre>
  
  <p>Turns into when calling <code>response.json(user)</code></p>
  
  <pre><code>{
    "id": null,
    "shortLivedToken": "abcde",
    "longLivedToken": "fghji",
    "updated_at": "2015-11-21T18:32:20.181Z",
    "created_at": "2015-11-21T18:32:20.181Z"
  }
  </code></pre>
  
  <p>And I want it to be </p>
  
  <pre><code>{
    "id": null,
    "short_lived_token": "abcde",
    "long_lived_token": "fghij",
    "updated_at": "2015-11-21T18:32:20.181Z",
    "created_at": "2015-11-21T18:32:20.181Z"
  }
  </code></pre>
  
  <p>Any ideas?</p>