title: Sequelize Migration: update model after updating column attributes
body: <p>I will get through to the point already. I'm having a problem of updating the rows after I have changed the status column attribute.</p>
  
  <pre><code>up: function(queryInterface, Sequelize) {
      return queryInterface.changeColumn('projects', 'status', {
          type: Sequelize.ENUM('processing', 'unassigned', 'ongoing', 'completed'),
          allowNull: false,
          defaultValue: 'unassigned'
      }).then(function() {
          return Project.update({
              status: 'unassigned'
          }, {
              where: {
                  status: 'processing'
              }
          });
      });
  }
  </code></pre>
  
  <p>The Project.update() seems not working in any case but changing the attributes of the column works. </p>
  
  <p>Any idea guys? I'm somehow a newbie in sequelize and any idea would be a great help. Thanks.</p>