Use rounding for quarantine

Replaces flooring in quarantine by rounding.

The tests here still pass. The r.pops.spread test requires adjustment which can be previewed here: #218

include/pops/quarantine.hpp

@@ -147,20 +147,20 @@ class QuarantineEscapeAction
         DistDir closest;
         if (directions_.at(Direction::N)
             && (i - n) * north_south_resolution_ < mindist) {
-            mindist = static_cast<int>(std::floor((i - n) * north_south_resolution_));
+            mindist = std::lround((i - n) * north_south_resolution_);
             closest = std::make_tuple(mindist, Direction::N);
         }
         if (directions_.at(Direction::S)
             && (s - i) * north_south_resolution_ < mindist) {
-            mindist = static_cast<int>(std::floor((s - i) * north_south_resolution_));
+            mindist = std::lround((s - i) * north_south_resolution_);
             closest = std::make_tuple(mindist, Direction::S);
         }
         if (directions_.at(Direction::E) && (e - j) * west_east_resolution_ < mindist) {
-            mindist = static_cast<int>(std::floor((e - j) * west_east_resolution_));
+            mindist = std::lround((e - j) * west_east_resolution_);
             closest = std::make_tuple(mindist, Direction::E);
         }
         if (directions_.at(Direction::W) && (j - w) * west_east_resolution_ < mindist) {
-            mindist = static_cast<int>(std::floor((j - w) * west_east_resolution_));
+            mindist = std::lround((j - w) * west_east_resolution_);
             closest = std::make_tuple(mindist, Direction::W);
         }
         return closest;