Comment and trailing-space changes.
Fix for putting long vars in POST URL.

The major part of this change is changing:
  requests.get(self.url, params=payload)
to
  requests.post(self.url, data=postdata)
so that the parameters are sent in the request body, not in the URL.

The payload code has been refactored, and the GET payload excludes the body_X keys; this could be considered bad/overkill?