title: Request pipe keeps a wrong header
body: <p>I've built a small app which downloads from a url and upload to another. Here is my code:</p>
  
  <pre><code>request(downloadRequest).pipe(request(uploadRequest));
  </code></pre>
  
  <p>So it is very simple but my first request needs authorization so it contains an Authorization header (Bearer) and the second one does not. However, this header remains still during the pipe and blocks the request (Authorization header not allowed). </p>
  
  <p>I've tried the following code:    </p>
  
  <pre><code>request(downloadRequest)
                .on('response', function(resp) {
                  delete resp.headers['Authorization'];
                })
  </code></pre>
  
  <p>But it did not work. Do you have any idea?</p>