Update Bukkit for Minecraft 1.5.1
Added the hasGravity method to Blocks. Adds BUKKIT-3832
Add Fish (Hook) entity to PlayerFishEvent. Adds BUKKIT-1025
Spigot
EMC POM Changes
Water flow not trigger chunk loads

Make BlockFromToEvent default cancel if the flow would trigger a chunk load.
PlayerDeathEvent.getItemsToKeep

Exposes a mutable array on items a player should keep on death