title: AFHttpClient invalid tokens in dictionary when using AFFormURLParameterEncoding
body: <p>I've looked through SO and Google and haven't found a similiar issue to this. I feel like the answer is staring me in the face and I just need another set of eyes. </p>
  
  <p>I'm using AFNetworking to connect to the Stripe.com API. Specifically I'm using AFHTTPClient postPath to send data to an endpoint, charges. Stripe requires the request to be encoded as application/x-www-form-urlencoded so I can't use JSON encoding.</p>
  
  <p>The problem I'm running into is that I have a Charge object and a Card object. Card is a property on Charge and I convert both Charge and Card to NSDictionary's (Card is an dictionary inside of the Charge dictionary) and then pass them in as the parameters on the request like so:</p>
  
  <pre><code>NSDictionary *parameters = [ChargeRequest convertToDictionary:request];
  
  [[StripeAPIClient sharedClient] postPath:@"charges" parameters:parameters 
  success:^(AFHTTPRequestOperation *operation, id responseObject) 
  {        
      NSLog(@"Response: %@", responseObject);
  } 
  failure:^(AFHTTPRequestOperation *operation, NSError *error) {        
      NSLog(@"Error: %@", [error localizedDescription]);
      NSLog(@"Response: %@", operation.responseString);
  }];
  </code></pre>
  
  <p>When I do this, with AFHttpClient's parameterEncoding property set to AFFormURLParameterEncoding, Stripe returns this error:</p>
  
  <pre><code>"error": {
      "message": "Invalid token id: {\n    \"exp_month\" = 10;\n    \"exp_year\" = 2016;\n      number = 4242111111111111;\n}",
      "type": "invalid_request_error"
  }
  </code></pre>
  
  <p>The values in the error are specifically the key/values on the Card object after converting it. Here is the code I use for the conversion:</p>
  
  <pre><code>   return [[NSDictionary alloc] initWithObjectsAndKeys:request.number, @"number", [NSNumber numberWithInt:10], @"exp_month", [NSNumber numberWithInt:2016], @"exp_year", nil];
  </code></pre>
  
  <p>Any advice on what do to get rid of the invalid tokens being put in this NSDictionary? Am I focusing on the wrong thing? </p>
  
  <p>Thanks!</p>