title: how to use Alamofire with custom headers
body: <p>I am just starting to take a look at Mattt's wonderful new Alamofire swift networking library and am not quite sure how one would use it with custom headers. </p>
  
  <p>The code i am trying to convert from AFNetworking to Alamofire is this:</p>
  
  <pre><code>let request = NSMutableURLRequest(URL: url)
  request.setValue(authorizationToken, forHTTPHeaderField:"Authorization")
  </code></pre>