Add status code to ApiResponse

We weren't setting this before.

Octokit/Http/IResponse.cs

@@ -1,14 +1,21 @@
 using System;
 using System.Collections.Generic;
+using System.Net;
 
 namespace Octokit.Http
 {
-    public interface IResponse<T>
+    public interface IResponse<T> : IResponse
     {
+        new T BodyAsObject { get; set; }
+    }
+
+    public interface IResponse
+    {
+        object BodyAsObject { get; set; }
         string Body { get; set; }
-        T BodyAsObject { get; set; }
         Dictionary<string, string> Headers { get; }
         Uri ResponseUri { get; set; }
         ApiInfo ApiInfo { get; set; }
+        HttpStatusCode StatusCode { get; set; }
     }
 }