title: 400 Bad Request when adding utf-8 charset to POST request
body: <p>I've build an API client based on Guzzle that since version 3.4.2 adds an utf-8 charset to the Content-Type header. With this header the Asana API returns a 400 Bad Request error, while without the charset things work fine. </p>
  
  <p>This doesn't work on POST and PUT requests: </p>
  
  <blockquote>
    <p>Content-Type: application/x-www-form-urlencoded; charset=utf-8</p>
  </blockquote>
  
  <p>This works: </p>
  
  <blockquote>
    <p>Content-Type: application/x-www-form-urlencoded;</p>
  </blockquote>
  
  <p>Using curl as the simplest example :</p>
  
  <p>This one fails:</p>
  
  <pre><code>curl -u {apikey}: https://app.asana.com/api/1.0/projects -d "name=Test" -d "notes=Test." -d "workspace={workspace-id}" --header "Content-Type: application/x-www-form-urlencoded; charset=utf-8"
  </code></pre>
  
  <p>Returns a 400 Bad Request with this output : </p>
  
  <blockquote>
    <p>{"errors":[{"message":"Request data must be a JSON object, not null"}]}</p>
  </blockquote>
  
  <p>This one succeeds:</p>
  
  <pre><code>curl -u {apikey}: https://app.asana.com/api/1.0/projects -d "name=Test" -d "notes=Test." -d "workspace={workspace-id}" --header "Content-Type: application/x-www-form-urlencoded;"
  </code></pre>
  
  <p>This returns a 201 created with the data that was send.</p>
  
  <p>This happens for other POST and PUT requests as well. 
  Is this a bug in the Asana API or expected behaviour?</p>