py: Fix range to support negative step

[corona10]

Fixes: #41

[codecov-io]

Codecov Report

Merging #42 into master will increase coverage by 0.04%.
The diff coverage is 100%.

@@ Coverage Diff @@## master #42 +/- ## ========================================== + Coverage 65.91% 65.95% +0.04%  ========================================== Files 57 57 Lines 10206 10208 +2 ========================================== + Hits 6727 6733 +6 + Misses 3005 3002 -3 + Partials 474 473 -1

Impacted Files	Coverage Δ
py/range.go	81.81% <100%> (+6.81%)	⬆️

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[corona10]

@ncw Please take a look :)

[ncw]

I think the code looks fine - can you fix the conflict though?

[corona10]

@ncw
Done!
Thanks for the quick review, I hope you had happy Christmas with your family!

[ncw]

That looks great - thanks!

Unfortunately Santa gave me and my whole family Norovirus so I guess we must have been on the naughty list after all! We've recovered now though. I hope your Christmas was better :-)