Changed rule so that dead cells do not turn into zombie;

Example:
```diff
diff --git glider-gun.js glider-gun.js
index 8a2c5ed..df1fe41 100644
--- glider-gun.js
+++ glider-gun.js
@@ -2,7 +2,7 @@
 module.exports =
   "00000000000000000000000001\n" +
   "00000000000000000000000101\n" +
-  "0000000000000110000001100000000000011\n" +
+  "000000000000011000000!100000000000011\n" +
   "0000000000001000100001100000000000011\n" +
   "01100000000100000100011\n" +
   "01100000000100010110000101\n" +
```