title: GROUP BY and COUNT using ActiveRecord
body: <p>Refering to this:
  <a href="https://stackoverflow.com/questions/164319/is-there-any-difference-between-group-by-and-distinct">Is there any difference between GROUP BY and DISTINCT</a></p>
  
  <pre><code>Given a table that looks like this:
  
  name
  ------
  barry
  dave
  bill
  dave
  dave
  barry
  john
  This query:
  
  SELECT name, count(*) AS count FROM table GROUP BY name;
  Will produce output like this:
  
  name    count
  -------------
  barry   2
  dave    3
  bill    1
  john    1
  </code></pre>
  
  <p>What is the correct Rails convention here for ActiveModel to perform a GROUP BY with COUNT?</p>