title: Create or Update Sequelize
body: <p>I'm using Sequelize in my Nodejs project and I found a problem that I'm having a hard time to solve.
  Basically I have a cron that gets an array of objects from a server than inserts it on my database as a object ( for this case, cartoons ). But if I already have one of the objects, I have to update it.</p>
  
  <p>Basically I have a array of objects and a could use the BulkCreate() method. But as the Cron starts again, it doesn't solve it so I was needing some sort of update with an upsert true flag. And the main issue: I must have a callback that fires just once after all these creates or updates. Does anyone have an idea of how can I do that? Iterate over an array of object.. creating or updating it and then getting a single callback after?</p>
  
  <p>Thanks for the attention </p>