Correct the keySort() example

[mrattfeldt]

The permutation argument reflects the sorted position (1 based) of the
i:th element in vars.

Fixes # .

Changes proposed in this PR:

@chocoteam/core-developer

[codecov-io]

Codecov Report

Merging #678 into master will increase coverage by 0.07%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #678      +/-   ##
============================================
+ Coverage     62.73%   62.81%   +0.07%     
- Complexity    10196    10208      +12     
============================================
  Files           643      643              
  Lines         41121    41121              
  Branches       7863     7863              
============================================
+ Hits          25798    25829      +31     
+ Misses        12963    12936      -27     
+ Partials       2360     2356       -4     

Impacted Files	Coverage Δ	Complexity Δ
...lver/solver/constraints/IIntConstraintFactory.java	73.65% <ø> (ø)	195.00 <0.00> (ø)
...olver/solver/constraints/nary/nvalue/PropAMNV.java	70.00% <0.00%> (-20.00%)	5.00% <0.00%> (-2.00%)
...ch/strategy/selectors/variables/ActivityBased.java	79.00% <0.00%> (+1.00%)	61.00% <0.00%> (+1.00%)
...olver/solver/constraints/set/PropIntersection.java	91.57% <0.00%> (+3.15%)	36.00% <0.00%> (+1.00%)
...ver/solver/constraints/binary/PropDistanceXYC.java	76.43% <0.00%> (+7.47%)	61.00% <0.00%> (+8.00%)
...main/java/org/chocosolver/util/objects/MapVal.java	100.00% <0.00%> (+100.00%)	6.00% <0.00%> (+6.00%)

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[cprudhom]

Travis fails, but it has to do with something else (I think the right to run some specific steps in the script). So I force PR merge.