Build for specific Bukkit release:

Eliminates awkward situations of changes causing confusion when suddenly
your plugin won't compile on new versions of Bukkit. Stuck to 1.7.9-R0.2
because this is the last release supporting getOnlinePlayers as an array,
which this plugin builds against, and building this way supports the most
servers, which is always an admirable goal. Wouldn't want to force people
onto the latest dev, would we?
Substantially reduce disk IO in mass destruction:

Previously, the signs config file was saved for every single change to its
contents. This works great until you have an episode of mass destruction.
Suddenly, you're getting the file saved multiple times per tick. Goodbye,
TPS. Hello, lag.

This commit replaces the functionality of the saveSigns method with
flagging the signs config as requiring a save. A scheduled task checking
for this boolean once per second allows for up-to-the-second accuracy of
the config file without substantially compromising server stability.

Lastly, the config is saved in onDisable to ensure the task hasn't missed
anything.
Start update checking immediately:

Initializing the Updater class from the main thread allows the Updater
thread to begin its query before the first server tick, which is when the
scheduled task will begin. Gotta get that update!
Reduce File creation:

No, not file creation. File object creation!
Delete Vault if UUID file exists, not name