title: bookshelf js save() command not updating rows in postgresql db
body: <p>JS beginner trying to get a PostgreSQL DB talking to express.js through bookshelf.js.</p>
  
  <p>github: <a href="https://github.com/duskyshelf/bookers-academy/blob/master/booker.js">https://github.com/duskyshelf/bookers-academy/blob/master/booker.js</a></p>
  
  <pre><code>var knex = require('knex')({
    client: 'pg',
    connection: "postgres://localhost/bookers"
  });
  
  var bookshelf = require('bookshelf')(knex);
  
  var User = bookshelf.Model.extend({
    tableName: 'users'
  });
  
  var bob = new User({id: 2});
  bob.save()
  </code></pre>
  
  <p>bookshelf.js seems unable to add any content to the db.</p>
  
  <p>Current error message is: "Unhandled rejection CustomError: No Rows Updated'</p>