Sorted sets missing blocking operations

[JensErat]

Redis knows following blocking commands on sorted sets, similar to the ones on lists (which are already implemented in MiniRedis):

• BZMPOP
• BZPOPMAX
• BZPOPMIN

They behave similarly to zmpop, zpopmax, zpopmin, but wait for a timeout if no elements exist.

[alicebob]

Good point, thanks for the notice. I'll put it on the list, but of course PRs make things go much faster.