Bukkit Plugin Hunger Bar Games Error

14:41:21 [SEVERE] Could not load 'plugins/HungerBarGames.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: me/tomjw64/HungerBarGames/HungerBarGames : Unsupported major.minor version 51.0
	at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:150)
	at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:305)
	at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:230)
	at org.bukkit.craftbukkit.CraftServer.loadPlugins(CraftServer.java:207)
	at org.bukkit.craftbukkit.CraftServer.reload(CraftServer.java:541)
	at org.bukkit.Bukkit.reload(Bukkit.java:182)
	at org.bukkit.command.defaults.ReloadCommand.execute(ReloadCommand.java:22)
	at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:166)
	at org.bukkit.craftbukkit.CraftServer.dispatchCommand(CraftServer.java:473)
	at org.bukkit.craftbukkit.CraftServer.dispatchServerCommand(CraftServer.java:469)
	at net.minecraft.server.MinecraftServer.b(MinecraftServer.java:596)
	at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:565)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:449)
	at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)
Caused by: java.lang.UnsupportedClassVersionError: me/tomjw64/HungerBarGames/HungerBarGames : Unsupported major.minor version 51.0
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
	at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
	at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:41)
	at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:29)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:247)
	at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:139)
	... 13 more