Nerf shiver's health and teleportation

- Shiver's base health decreased from 350 to 250;
- Shiver can't teleport while headless.

sources/Zeds/Nice/NiceZombieShiver.uc

@@ -313,6 +313,7 @@ simulated function Tick(float Delta)
 //can't teleport if set on fire
 function bool CanTeleport()
 {
+    if (HeadHealth <= 0) return false;
     return !bFlashTeleporting && !bOnFire && Physics == PHYS_Walking && Level.TimeSeconds > TeleportBlockTime 
        && LastFlashTime + 7.5 < Level.TimeSeconds && !bIsStunned;
 }

sources/Zeds/Nice/NiceZombieShiverBase.uc

@@ -91,8 +91,8 @@ defaultproperties
     WaterSpeed=100.000000
     AccelRate=1024.000000
     JumpZ=340.000000
-    HealthMax=650.000000
-    Health=350
+    HealthMax=250.000000
+    Health=250
     MenuName="Shiver"
     MovementAnims(0)="ClotWalk"
     AmbientSound=SoundGroup'ScrnZedPack_S.Shiver.ShiverIdleGroup'