code: func (c *Client) ReadingsByDevice(id string, limit int) (readings []contract.Reading, err error) {
  	conn := c.Pool.Get()
  	defer conn.Close()
  
  	objects, err := getObjectsByRange(conn, db.ReadingsCollection+":device:"+id, 0, limit-1)
  	if err != nil {
  		if err != redis.ErrNil {
  			return readings, err
  		}
  	}
  
  	readings = make([]contract.Reading, len(objects))
  	for i, in := range objects {
  		err = unmarshalObject(in, &readings[i])
  		if err != nil {
  			return readings, err
  		}
  	}
  
  	return readings, nil
  }
docs: // Return a list of readings for the given device (id or name)
  // 404 - meta data checking enabled and can't find the device
  // Sort the list of readings on creation date