Update spell.js

Updated Penance damage/direct heal base and spellpower coefficient constants to bring them in line with Patch 5.3 data.  The new data already reflects the factors below, so I removed the 0.9/1.1 factors from "Penance - Damage" and "Penance - Heal" calculations that I added earlier.

Patch 5.3: Penance now deals 10% less damage, but healing done is increased by 10%.

Source for the values: http://www.wowhead.com/spell=47540.  Verified against combat logs.