Added Reds Cluster support to redis-copy script

[jadbox]

In addition, you can specify the destination table, clustering supports table merging strategies and you can manually specify prefix values to destination keys.

[grvhi]

Useful for me, thank you!

FYI, there's a small bug: the clustered value passed to main() on line 345 needs to be an int(). Alternatively, line 226 should be if self.clustered == "0":

Same goes for toTable

[salimane]

@jadbox any update on this ? Thanks