v1.3 - Huge update, read description

Huge code cleanup.
Changed prefix: false to prefix: 0 to disable the prefix.
Changed customMessage and customMessageForKiller variables (allow more
colour changes within the message (currencySymbol etc.)).
Removed hard coded colour for currencySymbol (included colour code in
customMessage or customMessageForKiller).
Removed useCurrencySymbol as it was unnecessary.
Bug fix causing pvpCost to inconsistently detect whether a player caused
their death.
New feature (Now allows a player to earn currency when killing another
player (pvpCost must be true)). Set pvpPay to 0 to disable.
New feature (A custom message when a player kills another player. Check
config for supported variables.(pvpCost must be true)).
New feature (Minimum amount of currency a player has to have before they
no can longer be affected by the percentage or flat amount in the
config.).
New feature (Set a flat amount that will be deducted from a players
account when they die and have less than or equal to the minimum amount
for penalty)