code: func (c *Conn) IndicesExists(indices ...string) (bool, error) {
  	var url string
  	if len(indices) > 0 {
  		url = fmt.Sprintf("/%s", strings.Join(indices, ","))
  	}
  	_, err := c.DoCommand("HEAD", url, nil, nil)
  	if err != nil {
  		if err == RecordNotFound {
  			return false, nil
  		} else {
  			return true, err
  		}
  	}
  	return true, nil
  }
docs: // IndicesExists checks for the existence of indices. uses RecordNotFound message if it doesn't exist and
  // "no error" situation if it exists. If there is some other error, gives the error and says it exists
  // just in case
  // see http://www.elasticsearch.org/guide/reference/api/admin-indices-indices-exists/