title: Sequelize: Change column type to ENUM
body: <p>I cannot seem to find the proper way to change a column from a String type to an ENUM while persisting the data in that column.</p>
  
  <p>I've also attempted to create a new column with the ENUM type and then copy the data between columns:</p>
  
  <pre><code>// migrations/20160606170538-change-column.js
  
  'use strict';
  
  module.exports = {
    up: function (queryInterface, Sequelize) {
      return queryInterface.addColumn('time', 'newcolumn', {
        allowNull: true,
        type: Sequelize.ENUM('1-day', '7-day', '1-month', '3-month', '6-month', '1-year')
      }).then(function () {
        return queryInterface.sequelize.query("UPDATE time SET newcolum = oldcolumn");
      });
    },
  
    down: function (queryInterface, Sequelize) {
    }
  };
  </code></pre>
  
  <p>But I return the following error on migration:</p>
  
  <blockquote>
    <p>error: column "newcolumn" is of type enum_time_newcolumn but expression is of type character varying]</p>
  </blockquote>