time slice in samples

[mufernando]

I always seem to want to get samples from a tree sequence within a time slice. Although this is not hard to do, I thought more people might be running into this situation and we could add a start_time and end_time argument to TreeSequence.samples(). This could be done just on the Python API end with a simple boolean mask applied on top of the array (the same way we do it for populations), see here.

Let me know if you think this is worth implementing and I can work on a PR.

[jeromekelleher]

I like it! My only hesitancy is about the names of the parameters --- would min_time and max_time be better? "start" and "end" imply a process, but we're not simulating here. max and min have an unambiguous interpretation in terms of the values of the time array.

[mufernando]

I really like the idea of min/max as names for the parameters. Will work on a PR.