Bukkit

What steps will reproduce the problem?
1. Load the plugin in the server.
2. Add the %achievements% variable in the public achievement message.
3. Get an achievement

What is the expected output? What do you see instead?
I would expect a message in the chat that I completed the achievement, but there isn't a message broadcasted and there appears an error in the console.

What version of Achievements are you using?
2.0.0

What version of Stats are you using?
2.0.1

Do you have an error log of what happened? If so, please provide it here using a pasting service.
http://pastebin.com/MQkXup4z

Please provide any additional information below.
There are no errors when I start the server (very recent Spigot 1.8 build). There is an another error caused by the same problem: Caused by: java.lang.NoClassDefFoundError: net/minecraft/util/com/google/gson/Gson (I'll create an another ticket for that).