title: Postgres: Order by string column with known values
body: <p>I have an <code>events</code> table with a <code>state</code> column. If everything goes according to plan, the states can only be one of:</p>
  
  <ul>
  <li><code>scheduled</code></li>
  <li><code>invited</code></li>
  <li><code>notified</code></li>
  <li><code>started</code></li>
  <li><code>ended</code></li>
  </ul>
  
  <p>Is it possible to order by <code>state</code> and specify which value comes first, second, third, etc...?</p>
  
  <p><strong>Bonus Points:</strong> Is there a way to do this easily in Rails 3?</p>