This update was mainly released to address a very serious memory leak in conjunction with Spigot. If you're using Spigot or one of its derivatives, I urge you to update as soon as possible. When loading and unloading worlds in succession, ProtocolLib would incorrectly retain a reference to each of these worlds, which would eventually exhaust all available memory to the JVM (and server). This has now been fixed.
It's now also possible to suppress warnings and errors by editing the configuration, should the need arise. It's probably most useful for people that are running a modded CraftBukkit server, and occasionally get irrelevant warnings and errors in the console.
There's also been a couple of other very minor bug fixes. See the change log for more details.