zscore list copy

#zscore, zrevrange

https://stackoverflow.com/questions/9282822/is-it-possible-to-duplicate-a-redis-sorted-set#

http://redis.io/commands/zunionstore

zadd foo 1 a
zadd foo 2 b
zunionstore bar 1 foo
zrange bar 0 -1
1) "a" 
2) "b"