title: AFNetworking 2.0 // How to read response header
body: <p>I'm using the new version of AFNetworking and I can't figure out how to read the headers of the response.
  I'm using the AFHTTPSessionManager to perform my query, everything works well but I'm unable to find the header response field.</p>
  <p>Here is how I proceed</p>
  <pre><code>self.sessionManager = [[AFHTTPSessionManager alloc] initWithBaseURL:[NSURL URLWithString:BASE_URL]];
  [self.sessionManager GET:urlId parameters:nil
      success:^(NSURLSessionDataTask *task, id responseObject) {
          if ([self.delegate respondsToSelector:@selector(userIsLoadedWithInfos:)]) {
              [self.delegate userIsLoadedWithInfos: responseObject];
          }
      } failure:^(NSURLSessionDataTask *task, NSError *error) {
          if ([self.delegate respondsToSelector:@selector(userLoadingFailed)]) {
              [self.delegate userLoadingFailed];
          }
      }
  ];
  </code></pre>
  <p>I tried to read the response attribute of task but it return an NSURLResponse which doesn't include the headers.</p>
  <p>Does anyone now how to read the response headers with the 2.0 version?</p>