title: Error in adding AFNetworking framework in the project
body: <p>Adding AFNetworking framework in the project I got the following errors:-</p>
  
  <pre><code>Undefined symbols for architecture i386:
    "_UTTypeCopyPreferredTagWithClass", referenced from:
        _AFContentTypeForPathExtension in AFURLRequestSerialization.o
    "_UTTypeCreatePreferredIdentifierForTag", referenced from:
        _AFContentTypeForPathExtension in AFURLRequestSerialization.o
    "_kUTTagClassFilenameExtension", referenced from:
        _AFContentTypeForPathExtension in AFURLRequestSerialization.o
    "_kUTTagClassMIMEType", referenced from:
        _AFContentTypeForPathExtension in AFURLRequestSerialization.o
  ld: symbol(s) not found for architecture i386
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  </code></pre>
  
  <p>I am using xcode 4.5 with sdk iOS 6.0</p>