Updated monster.json - buffed all zombies hp.

As per the forum discussion on: http://smf.cataclysmdda.com/index.php?topic=5176.30

All hp has been buffed by roughly 20-30 points, although lower in a few cases where I felt the monster was already hard enough. Hulks were buffed by 100hp, as a lot of people seem to complain they're too soft..