title: Create Item in Podio Using Python Wrapper PyPOdio
body: <p>I am unable to create an item in PODIO using PYPODIO2 wrapper and the API. I have been able to successfully authorise using OAuth App Authentication. 
  Below is the snippet of code that i am trying to execute but i run into an error</p>
  
  <pre><code>attributes={"fields": {"module-serial": serial_number,
                         "contract-manufacturer-name-2":"Extel",
                         "module-number-and-name":{ 
                                  "status": "active",
                                  "text": "BD201: Main Board Extended Build",
                                  "id": 2},
                         "category":{
                                 "status": "active",
                                 "text": "Pass",
                                 "id": 1}
                         }
              }
  
  pcbapp.Item.create(17174065, attributes)
  </code></pre>
  
  <blockquote>
    <p><strong>Error:</strong> pypodio2.transport.TransportException:
    TransportException({'server': 'nginx', 'date': 'Tue, 07 Feb 2017
    05:49:05 GMT', 'content-type': 'application/json; charset=utf-8',
    'content-length': '259', 'connection': 'keep-alive',
    'x-rate-limit-remaining': '989', 'x-rate-limit-limit': '1000',
    'x-podio-auth-ref': 'app_17174065', 'x-podio-request-id': 'yUWqV1ao',
    'strict-transport-security': 'max-age=31535999', 'status': '400'}):
    {"error_parameters":{},"error_detail":null,"error_propagate":false,"request":{"url":"http://api.podio.com/item/app/17174065/","query_string":"","method":"POST"},"error_description":"Invalid
    value null (null): Not a valid option","error":"invalid_value"}</p>
  </blockquote>
  
  <p>Error description: <code>Invalid value null (null): Not a valid option</code></p>