add zpopmax/min and blocking variants

[r2evans]

No description provided.

[r2evans]

The codecov problems are not from my patch, other checks appear good.

[richfitz]

The interface is generated from the redis spec, and there's an open PR which implements this (and many other new methods) here: https://github.com/richfitz/redux/pull/41/files

However, I am not at all happy with the log interface (X*) and need to get some feedback from someone with a need to use them. If I get time I will exclude these and can move towards merging what is there, which should fix this.

If you need these methods, would you mind testing that branch for me?

[r2evans]

I didn't see #41 (and I was in a rush on one project, implemented basically what I needed), sorry about the duplicate effort and noise. Now I see and better understand extra/generate*.R. (Nice, auto-generating ... would be great to be able to autogen tests too based on their demo/tests, perhaps a thought for another day/issue/PR :-)

I have read a little about the X* log/stream functions (and have a little experience with Kafka). I'll pick up the conversation in 41, since that's where your concerns are first stated and will be resolved.