title: sequelize.js TIMESTAMP not DATETIME
body: <p>In my node.js app I have several models in which I want to define <code>TIMESTAMP</code> type columns, including the default timestamps <code>created_at</code> and <code>updated_at</code>. </p>
  
  <p>According to <a href="http://docs.sequelizejs.com/en/latest/api/datatypes/">sequelize.js' documentation</a>, there is only a <code>DATE</code> data type. It creates <code>DATETIME</code> columns in MySQL.</p>
  
  <p>Example:</p>
  
  <pre><code>var User = sequelize.define('User', {
  ... // columns
  last_login: {
              type: DataTypes.DATE,
              allowNull: false
          },
  ...
  }, { // options
          timestamps: true
  });
  </code></pre>
  
  <p>Is it possible to generate <code>TIMESTAMP</code> columns instead?</p>