Add indices arg to remaining selection operators

[SigmaX]

We've found it useful at least twice now to have selection operators that are able to return, not just an individual, but the index of that individual within the population.

This should become our new standard interface. We've already added an indices argument (which takes an empty list that the index is added to) to ops.naive_cyclic_selection(), ops.random_selection(), and to ops.tournament_selection().

Remaining operators that should support an indices argument:

• ops.proportional_selection()
• ops.sus_selection()
• ops.truncation_selection()
• ops.insertion_selection()
• ops.cyclic_selection()

[markcoletti]

This is an interesting development, and I can see where this would be useful.

Somewhere in the code I have some kind of one-liner for returning the index of a selected individual that I got from stackoverflow that could potentially be useful for some of these other operators. I'm not near the source right now, though, so I'll have to grep for it later.