QuickSortInPlace: bug in performance measuring code.

[haalogen]

Hey guys,

javascript-algorithms/src/algorithms/sorting/quick-sort/QuickSortInPlace.js

Line 49 in 1f39355

this.callbacks.visitingCallback(array[pivot]);

pivot is meant to be a value, isn't it?
Shouldn't it be

 this.callbacks.visitingCallback(array[highIndex]); 

or

 this.callbacks.visitingCallback(pivot); 

instead?

This change is also proposed in: #239

[trekhleb]

@haalogen yes, you're right. Thank you for the fix!