title: undefined method `digest' with rails 4.0.1
body: <p>I'm going through <code>Agile Web Development With Rails 4</code> and have got to the point where I create a user. It's being done like so:</p>
  
  <pre><code>rails generate scaffold User name:string password:digest
  </code></pre>
  
  <p>But when I try to run <code>rake db:migrate</code> I get the following error: <code>undefined method digest'</code></p>
  
  <p>What is the cause of that and how can I fix it? I googled that <code>digest</code> is a <code>rails 4</code> feature, so how come it's an issue?</p>