title: ElasticSearch + Tire: OR query
body: <p>I have some trouble defining a query with Tire.</p>
  
  <p><strong>What I have:</strong></p>
  
  <p>My documents are events. They have a <code>starts_at</code> date, and a <code>ends_at</code> date.
  The <code>ends_at</code> date is not required.</p>
  
  <p><strong>What I want:</strong></p>
  
  <p>I want to display upcoming events (for instance). I would define <code>upcoming</code> as the following:</p>
  
  <ul>
  <li><code>ends_at</code> date is present AND after Time.now</li>
  </ul>
  
  <p>OR</p>
  
  <ul>
  <li><code>ends_at</code> date is not present, AND <code>starts_at</code> is after Time.now</li>
  </ul>
  
  <p>Right now I'm just doing</p>
  
  <pre><code>query do
      boolean do
          must { range :starts_at, { gte: bod } }
      end
  end
  </code></pre>
  
  <p>How can I this OR query?</p>