[Feature Request] Add the ability to set a minimum number of responding stations #99

It is valuable to work on pulling calls out of a pileup, but the fixed logic for pileup probability can mean working a lot of single stations or small pileups when you want to work lots of stations.

A "minimum stations" configuration in parallel with "maximum stations" would help make it easier to get pileup practice, like this:

I have an implementation of this for which I plan to open a pull request.