Sorted for python 3

[anderspitman]

In order to generate test data that could be compared to a python 3 run of sisrs, a few changes were necessary. This mostly had to do with sorting things to make ordering deterministic. If it's decided to merge this, please look over the changes carefully to verify it won't change any important behavior or drastically affect performance or memory requirements.

[reedacartwright]

Alternatively, the tests can do the sorting, correct, instead of changing the algorithm?

[anderspitman]

@reedacartwright that could get quite involved. Not even sure how to approach it since most of the command perform multiple steps for a single output.

I think the changes here are minimal enough to be worth the risk. As far as I know they don't represent any semantic change in the output, only ordering.