Future plans: full snapshot support

[vorner]

Currently, the structures don't allow snapshots or consistent iteration through them. This makes the code simpler and probably a bit faster (though that is hard to confirm without a way to compare).

On the other hand, there certainly are use cases that would benefit from such feature. So it would be nice to allow that in the future.

My feeling is that it could make sense to actually have both implementations (either in the same crate, or in a separate). Maybe there's a way to share some code, though.

As I don't have this on top of the priority list, this is certainly free to be taken by anyone interested (claim the issue if you want to start working on it).