statsd.go
func (c *Client) Unique(bucket string, value string) {
	if c.skip() {
		return
	}
	c.conn.unique(c.prefix, bucket, value, c.tags)
}
func (c *Client) Unique(bucket string, value string) {
	if c.skip() {
		return
	}
	c.conn.unique(c.prefix, bucket, value, c.tags)
}
// Unique sends the given value to a set bucket.