message: Use std::accumulate instead of loop to add population
diff: #include "../RandomNumberGenerator.h"
  #include <algorithm>
  #include <iostream>
  +#include <numeric>
  namespace {
  @@ -67,12 +68,7 @@ void Population::addPopulation(PersonRole role, int count)
  */
  int Population::size() const
  {
  - int count = 0;
  - for (auto& populationRole : mPopulation)
  - {
  - count += populationRole;
  - }
  - return count;
  + return std::accumulate(mPopulation.begin(), mPopulation.end(), 0);
  }
  