Fix Register Command.

`[09:28:20] [Server thread/INFO]: [Trade] Enabling Trade v1.0-ALPHA
[09:28:20] [Server thread/INFO]: Updating plugins/Trade/messages.yml
[09:28:20] [Server thread/ERROR]: Error occurred while enabling Trade v1.0-ALPHA (Is it up to date?)
java.lang.NullPointerException
	at me.josvth.trade.CommandManager.initialize(CommandManager.java:25) ~[?:?]
	at me.josvth.trade.Trade.onEnable(Trade.java:75) ~[?:?]
	at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:250) ~[craftbukkit.jar:git-Bukkit-1.7.2-R0.3-2-g85f5776-b3024jnks]
	at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:324) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-2-g85f5776-b3024jnks]
	at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:404) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-2-g85f5776-b3024jnks]
	at org.bukkit.craftbukkit.v1_7_R1.CraftServer.loadPlugin(CraftServer.java:439) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-2-g85f5776-b3024jnks]
	at org.bukkit.craftbukkit.v1_7_R1.CraftServer.enablePlugins(CraftServer.java:375) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-2-g85f5776-b3024jnks]
	at net.minecraft.server.v1_7_R1.MinecraftServer.m(MinecraftServer.java:342) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-2-g85f5776-b3024jnks]
	at net.minecraft.server.v1_7_R1.MinecraftServer.g(MinecraftServer.java:319) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-2-g85f5776-b3024jnks]
	at net.minecraft.server.v1_7_R1.MinecraftServer.a(MinecraftServer.java:275) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-2-g85f5776-b3024jnks]
	at net.minecraft.server.v1_7_R1.DedicatedServer.init(DedicatedServer.java:175) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-2-g85f5776-b3024jnks]
	at net.minecraft.server.v1_7_R1.MinecraftServer.run(MinecraftServer.java:424) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-2-g85f5776-b3024jnks]
	at net.minecraft.server.v1_7_R1.ThreadServerApplication.run(SourceFile:617) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-2-g85f5776-b3024jnks]
[09:28:20] [Server thread/INFO]: [VanishNoPacket] Enabling VanishNoPacket v3.18.9`