Bukkit

General:
-Cleaned up the code a bit.
-Switched to using a queue for asynchronous player messages. It should slightly improve the efficiency.

For memory efficiency, only about 10 changes will be kept for any particular block.*

*The number recorded can actually be a bit higher than 10, since the ceiling for a deletion operation is actually 14 changes. In other words,
 the system won't actually delete any recorded changes until there are 14 or more changes for a particular block.