title: expand request parameter not working for Events API call
body: <p>I have been using Expand parameter for Charges API call and it was working fine.</p>
  
  <p>But when i used Expand parameter with Events call it gave error.
  I wanted to expand <code>Invoice</code> ID object.</p>
  
  <p>Following is the URL:</p>
  
  <pre><code>https://api.stripe.com/v1/events?type=charge.*&amp;count=100&amp;expand[]=data.invoice'
  </code></pre>
  
  <p>Following is the Error message:</p>
  
  <pre><code>[type] =&gt; invalid_request_error
  [message] =&gt; This property cannot be expanded (data.invoice).
  </code></pre>
  
  <p>I also tried to change value like <code>invoice</code> , <code>data.data.invoice</code> But no success. </p>
  
  <p>How can i get this to work ? Am i missing something ?</p>
  
  <p>Thanks,</p>