Bukkit

What steps will reproduce the problem?
1. I have no clue
2.
3.

What is the expected output? What do you see instead?
I just want the plugin to work, it doesn't show up in /pl

What version of the product are you using?
Lastest version up to this date.

Do you have an error log of what happened?
Could not load 'plugins/bGo.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: betrayed/go/BetrayGo : Unsupported major.minor version 51.0
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:131) ~[CraftBukkit.jar:git-Bukkit-1.7.2-R0.3-14-g8f8716c-b3042jnks]
    at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:328) ~[CraftBukkit.jar:git-Bukkit-1.7.2-R0.3-14-g8f8716c-b3042jnks]
    at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:251) [CraftBukkit.jar:git-Bukkit-1.7.2-R0.3-14-g8f8716c-b3042jnks]
    at org.bukkit.craftbukkit.v1_7_R2.CraftServer.loadPlugins(CraftServer.java:350) [CraftBukkit.jar:git-Bukkit-1.7.2-R0.3-14-g8f8716c-b3042jnks]
    at org.bukkit.craftbukkit.v1_7_R2.CraftServer.reload(CraftServer.java:784) [CraftBukkit.jar:git-Bukkit-1.7.2-R0.3-14-g8f8716c-b3042jnks]
    at org.bukkit.Bukkit.reload(Bukkit.java:288) [CraftBukkit.jar:git-Bukkit-1.7.2-R0.3-14-g8f8716c-b3042jnks]
    at org.bukkit.command.defaults.ReloadCommand.execute(ReloadCommand.java:23) [CraftBukkit.jar:git-Bukkit-1.7.2-R0.3-14-g8f8716c-b3042jnks]
    at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:180) [CraftBukkit.jar:git-Bukkit-1.7.2-R0.3-14-g8f8716c-b3042jnks]
    at org.bukkit.craftbukkit.v1_7_R2.CraftServer.dispatchCommand(CraftServer.java:696) [CraftBukkit.jar:git-Bukkit-1.7.2-R0.3-14-g8f8716c-b3042jnks]
    at org.bukkit.craftbukkit.v1_7_R2.CraftServer.dispatchServerCommand(CraftServer.java:683) [CraftBukkit.jar:git-Bukkit-1.7.2-R0.3-14-g8f8716c-b3042jnks]
    at net.minecraft.server.v1_7_R2.DedicatedServer.ax(DedicatedServer.java:286) [CraftBukkit.jar:git-Bukkit-1.7.2-R0.3-14-g8f8716c-b3042jnks]
    at net.minecraft.server.v1_7_R2.DedicatedServer.v(DedicatedServer.java:251) [CraftBukkit.jar:git-Bukkit-1.7.2-R0.3-14-g8f8716c-b3042jnks]
    at net.minecraft.server.v1_7_R2.MinecraftServer.u(MinecraftServer.java:548) [CraftBukkit.jar:git-Bukkit-1.7.2-R0.3-14-g8f8716c-b3042jnks]
    at net.minecraft.server.v1_7_R2.MinecraftServer.run(MinecraftServer.java:459) [CraftBukkit.jar:git-Bukkit-1.7.2-R0.3-14-g8f8716c-b3042jnks]
    at net.minecraft.server.v1_7_R2.ThreadServerApplication.run(SourceFile:618) [CraftBukkit.jar:git-Bukkit-1.7.2-R0.3-14-g8f8716c-b3042jnks]
Caused by: java.lang.UnsupportedClassVersionError: betrayed/go/BetrayGo : Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method) ~[?:1.6.0_65]
    at java.lang.ClassLoader.defineClassCond(ClassLoader.java:637) ~[?:1.6.0_65]
    at java.lang.ClassLoader.defineClass(ClassLoader.java:621) ~[?:1.6.0_65]
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141) ~[?:1.6.0_65]
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:283) ~[?:1.6.0_65]
    at java.net.URLClassLoader.access$000(URLClassLoader.java:58) ~[?:1.6.0_65]
    at java.net.URLClassLoader$1.run(URLClassLoader.java:197) ~[?:1.6.0_65]
    at java.security.AccessController.doPrivileged(Native Method) ~[?:1.6.0_65]
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190) ~[?:1.6.0_65]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:77) ~[CraftBukkit.jar:git-Bukkit-1.7.2-R0.3-14-g8f8716c-b3042jnks]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:62) ~[CraftBukkit.jar:git-Bukkit-1.7.2-R0.3-14-g8f8716c-b3042jnks]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306) ~[?:1.6.0_65]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247) ~[?:1.6.0_65]
    at java.lang.Class.forName0(Native Method) ~[?:1.6.0_65]
    at java.lang.Class.forName(Class.java:249) ~[?:1.6.0_65]
    at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:40) ~[CraftBukkit.jar:git-Bukkit-1.7.2-R0.3-14-g8f8716c-b3042jnks]
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:127) ~[CraftBukkit.jar:git-Bukkit-1.7.2-R0.3-14-g8f8716c-b3042jnks]
    ... 14 more

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