Add setTarget and getTarget to Slime.

src/main/java/org/bukkit/craftbukkit/entity/CraftSlime.java

@@ -4,6 +4,7 @@ import net.minecraft.server.EntitySlime;
 
 import org.bukkit.craftbukkit.CraftServer;
 import org.bukkit.entity.EntityType;
+import org.bukkit.entity.LivingEntity;
 import org.bukkit.entity.Slime;
 
 public class CraftSlime extends CraftLivingEntity implements Slime {
@@ -20,6 +21,20 @@ public class CraftSlime extends CraftLivingEntity implements Slime {
         getHandle().setSize(size, true);
     }
 
+    @Override
+    public void setTarget(LivingEntity target) {
+        if (target == null) {
+            getHandle().setGoalTarget(null, null, false);
+        } else if (target instanceof CraftLivingEntity) {
+            getHandle().setGoalTarget(((CraftLivingEntity) target).getHandle(), null, false);
+        }
+    }
+
+    @Override
+    public LivingEntity getTarget() {
+        return getHandle().getGoalTarget() == null ? null : (LivingEntity)getHandle().getGoalTarget().getBukkitEntity();
+    }
+
     @Override
     public EntitySlime getHandle() {
         return (EntitySlime) entity;