implemented fix_rank_range

[daef]

after some head scratching on how to fix the total order of a range of elements by fixing the order of single elements I've also come to the conclusion that it's at least easier to do it in one go (so the yet-to-be-sorted/unsorted elements can be ignored)

so I've implemented fix_rank_range to fix the positions for a range of elements.

and fix_index which allows to mutate indices that were obtained before the fix_rank operation to point to the same elements as they did before.

plus tarpaulin seems happy about the test :)

[codecov-commenter]

Codecov Report

Merging #2 into master will increase coverage by 0.14%.
The diff coverage is 96.38%.

@@            Coverage Diff             @@
##           master       #2      +/-   ##
==========================================
+ Coverage   96.17%   96.32%   +0.14%     
==========================================
  Files           1        1              
  Lines         497      517      +20     
==========================================
+ Hits          478      498      +20     
  Misses         19       19              

Impacted Files	Coverage Δ
lib/src/array_stump.rs	96.32% <96.38%> (+0.14%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update bf09fcf...d2ca898. Read the comment docs.

[bluenote10]

Sorry for the delay -- just returning from vacations and catching up on long list of GitHub activities. So skipping a detailed review, but on first glance that looks like something I had in mind in the 21re/rust-geo-booleanop#17 context.

[daef]

I suspected something along those lines and hope you've had a nice time :)