title: Using ajaxSetup beforeSend for Basic Auth is breaking SignalR connection
body: <p>I have a WebApi secured with Basic Auth which is applied to the entire Api using a AuthorizationFilterAttribute. I also have SignalR Hubs sitting on several of my Api Controllers.</p>
  
  <p>Alongside this I have a web page which makes use of my WebApi. The web page is mostly written in Backbone, so in order to make calls to my secured WebApi, I have added the following jquery</p>
  
  <pre><code>$.ajaxSetup({
      beforeSend: function (jqXHR, settings) {
          jqXHR.setRequestHeader('Authorization', 'Basic ' + Token);
          return true;
      }
  });
  </code></pre>
  
  <p>This works for communicating with my Api Controllers, but adding the above code has broken the connection to my SignalR Hubs, specifically:</p>
  
  <pre><code>XMLHttpRequest cannot load http://localhost:50000/signalr/negotiate?_=1366795855194. 
  Request header field Authorization is not allowed by Access-Control-Allow-Headers. 
  </code></pre>
  
  <p>Removing the <code>jqXHR.setRequestHeader()</code> line restores my SignalR Hub connection but breaks the Api calls.</p>
  
  <p>Given the above, I could do something hacky and only set the request header if the request being made isn't to /signalr but that just feels dirty...</p>
  
  <p>Is there a cleaner way around this?</p>
  
  <p>Am I just doing something silly? Has anyone else ran in to this?</p>