title: Return max value in a column with peewee
body: <p>I have a table called jobs with a column called job_num.
  How do i return the maximum value of the integers in that column?</p>
  
  <p>I have tried </p>
  
  <pre><code>result = Job.select(max(Job.job_num))
  </code></pre>
  
  <p>I have also tried a few different combinations such as </p>
  
  <pre><code>result = Job.select(Job.job_num).max()
  </code></pre>
  
  <p>I have also checked the peewee docs.
  Can anyone help please.</p>