SEVERE] Could not load 'plugins\Ranks.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: Me/Kostronor/Ranks/Ranks : Unsupported major.minor version 51.0
	at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:150)
	at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:287)
	at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:211)
	at org.bukkit.craftbukkit.CraftServer.loadPlugins(CraftServer.java:207)
	at org.bukkit.craftbukkit.CraftServer.<init>(CraftServer.java:183)
	at net.minecraft.server.ServerConfigurationManager.<init>(ServerConfigurationManager.java:53)
	at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:156)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:425)
	at net.minecraft.server.ThreadServerApplication.run(SourceFile:490)
Caused by: java.lang.UnsupportedClassVersionError: Me/Kostronor/Ranks/Ranks : Unsupported major.minor version 51.0
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClassCond(Unknown Source)
	at java.lang.ClassLoader.defineClass(Unknown Source)
	at java.security.SecureClassLoader.defineClass(Unknown Source)
	at java.net.URLClassLoader.defineClass(Unknown Source)
	at java.net.URLClassLoader.access$000(Unknown Source)
	at java.net.URLClassLoader$1.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(Unknown Source)
	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(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Unknown Source)
	at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:139)
	... 8 more