Bukkit

Hello, when i try installing Clear Lag version 2.7.1 on Bukkit 1.7.9-R0.1 it repeatedly shows this message when i load up my server. [10:35:50] [Server thread/INFO]: Starting minecraft server version 1.7.9
[10:35:50] [Server thread/INFO]: Loading properties
[10:35:50] [Server thread/INFO]: Default game type: SURVIVAL
[10:35:50] [Server thread/INFO]: Generating keypair
[10:35:50] [Server thread/INFO]: Starting Minecraft server on *:25565
[10:35:50] [Server thread/INFO]: This server is running CraftBukkit version git-Bukkit-1.7.9-R0.2-11-g3fd9db2-b3098jnks (MC: 1.7.9) (Implementing API version 1.7.9-R0.3-SNAPSHOT)
[10:35:51] [Server thread/ERROR]: Could not load 'plugins\Clearlag (1).jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: me/minebuilders/clearlag/Clearlag : Unsupported major.minor version 51.0
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:131) ~[craftbukkit.jar:git-Bukkit-1.7.9-R0.2-11-g3fd9db2-b3098jnks]
    at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:328) ~[craftbukkit.jar:git-Bukkit-1.7.9-R0.2-11-g3fd9db2-b3098jnks]
    at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:251) [craftbukkit.jar:git-Bukkit-1.7.9-R0.2-11-g3fd9db2-b3098jnks]
    at org.bukkit.craftbukkit.v1_7_R3.CraftServer.loadPlugins(CraftServer.java:364) [craftbukkit.jar:git-Bukkit-1.7.9-R0.2-11-g3fd9db2-b3098jnks]
    at org.bukkit.craftbukkit.v1_7_R3.CraftServer.<init>(CraftServer.java:326) [craftbukkit.jar:git-Bukkit-1.7.9-R0.2-11-g3fd9db2-b3098jnks]
    at net.minecraft.server.v1_7_R3.PlayerList.<init>(PlayerList.java:68) [craftbukkit.jar:git-Bukkit-1.7.9-R0.2-11-g3fd9db2-b3098jnks]
    at net.minecraft.server.v1_7_R3.DedicatedPlayerList.<init>(SourceFile:14) [craftbukkit.jar:git-Bukkit-1.7.9-R0.2-11-g3fd9db2-b3098jnks]
    at net.minecraft.server.v1_7_R3.DedicatedServer.init(DedicatedServer.java:126) [craftbukkit.jar:git-Bukkit-1.7.9-R0.2-11-g3fd9db2-b3098jnks]
    at net.minecraft.server.v1_7_R3.MinecraftServer.run(MinecraftServer.java:436) [craftbukkit.jar:git-Bukkit-1.7.9-R0.2-11-g3fd9db2-b3098jnks]
    at net.minecraft.server.v1_7_R3.ThreadServerApplication.run(SourceFile:628) [craftbukkit.jar:git-Bukkit-1.7.9-R0.2-11-g3fd9db2-b3098jnks]
Caused by: java.lang.UnsupportedClassVersionError: me/minebuilders/clearlag/Clearlag : Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method) ~[?:1.6.0_20]
    at java.lang.ClassLoader.defineClassCond(Unknown Source) ~[?:1.6.0_20]
    at java.lang.ClassLoader.defineClass(Unknown Source) ~[?:1.6.0_20]
    at java.security.SecureClassLoader.defineClass(Unknown Source) ~[?:1.6.0_20]
    at java.net.URLClassLoader.defineClass(Unknown Source) ~[?:1.6.0_20]
    at java.net.URLClassLoader.access$000(Unknown Source) ~[?:1.6.0_20]
    at java.net.URLClassLoader$1.run(Unknown Source) ~[?:1.6.0_20]
    at java.security.AccessController.doPrivileged(Native Method) ~[?:1.6.0_20]
    at java.net.URLClassLoader.findClass(Unknown Source) ~[?:1.6.0_20]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:77) ~[craftbukkit.jar:git-Bukkit-1.7.9-R0.2-11-g3fd9db2-b3098jnks]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:62) ~[craftbukkit.jar:git-Bukkit-1.7.9-R0.2-11-g3fd9db2-b3098jnks]
    at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.6.0_20]
    at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.6.0_20]
    at java.lang.Class.forName0(Native Method) ~[?:1.6.0_20]
    at java.lang.Class.forName(Unknown Source) ~[?:1.6.0_20]
    at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:40) ~[craftbukkit.jar:git-Bukkit-1.7.9-R0.2-11-g3fd9db2-b3098jnks]
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:127) ~[craftbukkit.jar:git-Bukkit-1.7.9-R0.2-11-g3fd9db2-b3098jnks]
    ... 9 more
This also shows when installing other plugins as well.
How do i fix this?
Thanks

Update to Java 7

rename the file to Clearlag.jar no need for the (1)