title: node sequelize sort by multiple columns
body: <p>Coming from a Ruby/Rails background, I'm used to this type of syntax:</p>
  
  <p><code>Model.all.order('col1 + col2 + col3')</code></p>
  
  <p>So, given that col1, col2 and col3 are integers, for example, it would sort the results by the sum of those 3 columns.</p>
  
  <p>Is there a similar way to sort like this using sequelize?</p>