title: Django Query to find number of rows with a certain value greater than zero, grouped by user
body: <p>I have a dataset such that each user has an integer as a score for each date in a certain date range.</p>
  
  <p>I want to find for each user, the number of days on which he/she had a greater than zero score - so, I want to <code>group by</code> user and <code>count</code> number of scores greater than zero for each user.</p>
  
  <p>How do I write such a query in Django 1.10?</p>