Create the URL to submit to the Steam Web API

        interface: Steam Web API interface containing methods.
        method: The method to call.
        version: The version of the method.
        paramters: Parameters to supply to the method.

def create_request_url(self, interface, method, version, parameters):
        """Create the URL to submit to the Steam Web API

        interface: Steam Web API interface containing methods.
        method: The method to call.
        version: The version of the method.
        paramters: Parameters to supply to the method.

        """
        if 'format' in parameters:
            parameters['key'] = self.apikey
        else:
            parameters.update({'key' : self.apikey, 'format' : self.format})
        version = "v%04d" % (version)
        url = "http://api.steampowered.com/%s/%s/%s/?%s" % (interface, method,
            version, urlencode(parameters))
        return url