Added option to not drop experience for instant kills.

src/main/java/com/songoda/ultimatestacker/entity/EntityStack.java

@@ -168,7 +168,7 @@ public class EntityStack {
                 EntityDamageEvent.DamageCause cause = lastDamageCause.getCause();
                 for (String s : reasons) {
                     if (!cause.name().equalsIgnoreCase(s)) continue;
-                    handleWholeStackDeath(killed, items, droppedExp);
+                    handleWholeStackDeath(killed, items, Setting.NO_EXP_INSTANT_KILL.getBoolean() ? 0 : droppedExp);
                     return;
                 }
             }

src/main/java/com/songoda/ultimatestacker/utils/settings/Setting.java

@@ -60,6 +60,9 @@ public enum Setting {
             "FALLING_BLOCK, THORNS, DRAGON_BREATH, CUSTOM",
             "FLY_INTO_WALL, HOT_FLOOR, CRAMMING, DRYOUT"),
 
+    NO_EXP_INSTANT_KILL("Entities.No Exp For Instant Kills", false,
+            "Should no experience be dropped when an instant kill is performed?"),
+
     STACK_CHECKS("Entities.Stack Checks", Arrays.asList(Check.values()).stream()
             .filter(Check::isEnabledByDefault).map(Check::name).collect(Collectors.toList()),
             "These are checks that are processed before an entity is stacked.",