Include gear defense in miss and crit chance.

Previously, the defense stat from gear was never saved.  For dodge, block
and parry, existing functions are used to access the accurate values from
the game directly, but crit and miss chances must be calculated.

Increase miss chance, and decrease crit chance, by gear defense * 0.04.

Fixes #11.
Remove duplicate application of bonus base defense.

When calculating block, dodge and parry chances, the actual base defense,
including where the skill is not completely leveled, is being used in lieu
of 5x the player level, when applying the level difference between player
and target to these stats.

Replace
    0.04x(5xtarget level - base def)
with
    0.04x(5x(target level - player level))
when determining by what amount to increase block, dodge and parry chances
based on level difference.

Fix #7.
Replace tabs with spaces.