Fix ice balance checks.

As discussed in #122. I *think* this fix works; at least, it worked in my
brief testing.

Also update ice checks to not try a balance check when you've already fallen
or if you're flying.
Merge pull request #147 from joshkel/ice-balance

Fix ice balance checks.
gameplay variant options screen
implement defensive roll variant
update features listing
can now attack while dying
working on barter
more progress on barter
give subtypes to neutral npcs
no more 'hits for 0 darkness damage' spam
implement fear