title: WCF not honoring RequestFormat
body: <p>Trying to create a simple WCF service that behaves as a restful endpoint.  Hoping someone can see what I'm missing.</p>
  
  <pre><code>[OperationContract]
  [WebInvoke(Method ="POST", UriTemplate = "TestJson", BodyStyle = WebMessageBodyStyle.Wrapped, RequestFormat = WebMessageFormat.Json, ResponseFormat = WebMessageFormat.Json)]
          string TestJson(CompositeType composite);
  </code></pre>
  
  <p>And From postman I get </p>
  
  <blockquote>
    <p>Cannot process the message because the content type 'application/json' was not the expected 'text/xml; charset=utf-8'</p>
  </blockquote>