Changed the initialization loop to be times.newParents; were getting
an off by 1 error by adding too many using the for(i in 0..numParents)
because numParents is inclusive.

refactored the loop where we add the top elements in
sortedIndividualArr to individualArr by setting individualArr equal to
sortedIndividualArr[0..<numParents]. pretty neat shortcut
Changed the child-making loop so that instead of looking at the size
of the array, it looks at numParents (which is more sensible and
readable than the alternative.