def push_single_device(device_token, message_type, message, params = {})
      params.merge!({
        device_token: device_token,
        message:      message,
        message_type: message_type
        })
      self.send_request('push','single_device',params)
    end
def push_single_device(device_token, message_type, message, params = {})
      params.merge!({
        device_token: device_token,
        message:      message,
        message_type: message_type
        })
      self.send_request('push','single_device',params)
    end
push消息（包括通知和透传消息）给单个设备