Introduce Poise stat

Closes #80

I went with a percentage chance here as opposed to a damage threshold
because I think it's easier to scale when balancing combat numbers. We can
always change the formula to a damage threshold later if that's the desired
method.

I decided to keep the hit sound effect when damage recoil is skipped, since
it's the only form of feedback when combat text is off.
Merge pull request #144 from matthiaskrgr/master

Items: change "AEther" (probably typo) to "Aether"
Merge pull request #322 from dorkster/bugfixes

Introduce Poise stat
Merge branch 'master' of https://github.com/clintbellanger/flare-engine
Cursed Grave: increase HP from 166 to 300. Aren't these made out of stone?
gitignore: try to improved entry order, add gmon.out
items: Aether Walkers -> Æther Walkers
Character appears to be supported by the used font.