private void validateArray(Integer[] numbers) {
    if (numbers == null) {
      throw new IllegalArgumentException("You can't pass a null array");
    }
  }
Slow implementation for this algorithm. First of all, sort the array using QuickSort algorithm
and then, go through the array and add to a list just those consecutive elements that are
different.

The complexity order of this algorithm in space terms is O(N) where N is the number of
elements in the input array. The complexity order in time terms is equals to the sorting
algorithm, O( N log(N)).
src/main/java/com/github/pedrovgs/problem10/RemoveDuplicates.java