[03:37:26] [Server thread/ERROR]: Could not load 'plugins/Skyotickets.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: fr/skyost/tickets/Skyotickets : Unsupported major.minor version 51.0
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:137) ~[craftbukkit_beta.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
    at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:313) ~[craftbukkit_beta.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
    at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:236) [craftbukkit_beta.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
    at org.bukkit.craftbukkit.v1_7_R1.CraftServer.loadPlugins(CraftServer.java:350) [craftbukkit_beta.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
    at org.bukkit.craftbukkit.v1_7_R1.CraftServer.reload(CraftServer.java:771) [craftbukkit_beta.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
    at org.bukkit.Bukkit.reload(Bukkit.java:279) [craftbukkit_beta.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
    at org.bukkit.command.defaults.ReloadCommand.execute(ReloadCommand.java:23) [craftbukkit_beta.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
    at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:175) [craftbukkit_beta.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
    at org.bukkit.craftbukkit.v1_7_R1.CraftServer.dispatchCommand(CraftServer.java:683) [craftbukkit_beta.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
    at org.bukkit.craftbukkit.v1_7_R1.CraftServer.dispatchServerCommand(CraftServer.java:670) [craftbukkit_beta.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
    at net.minecraft.server.v1_7_R1.DedicatedServer.aw(DedicatedServer.java:286) [craftbukkit_beta.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
    at net.minecraft.server.v1_7_R1.DedicatedServer.u(DedicatedServer.java:251) [craftbukkit_beta.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
    at net.minecraft.server.v1_7_R1.MinecraftServer.t(MinecraftServer.java:545) [craftbukkit_beta.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
    at net.minecraft.server.v1_7_R1.MinecraftServer.run(MinecraftServer.java:457) [craftbukkit_beta.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
    at net.minecraft.server.v1_7_R1.ThreadServerApplication.run(SourceFile:617) [craftbukkit_beta.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
Caused by: java.lang.UnsupportedClassVersionError: fr/skyost/tickets/Skyotickets : Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method) ~[?:1.6.0_27]
    at java.lang.ClassLoader.defineClass(ClassLoader.java:634) ~[?:1.6.0_27]
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) ~[?:1.6.0_27]
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:277) ~[?:1.6.0_27]
    at java.net.URLClassLoader.access$000(URLClassLoader.java:73) ~[?:1.6.0_27]
    at java.net.URLClassLoader$1.run(URLClassLoader.java:212) ~[?:1.6.0_27]
    at java.security.AccessController.doPrivileged(Native Method) ~[?:1.6.0_27]
    at java.net.URLClassLoader.findClass(URLClassLoader.java:205) ~[?:1.6.0_27]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:77) ~[craftbukkit_beta.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:62) ~[craftbukkit_beta.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:321) ~[?:1.6.0_27]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:266) ~[?:1.6.0_27]
    at java.lang.Class.forName0(Native Method) ~[?:1.6.0_27]
    at java.lang.Class.forName(Class.java:266) ~[?:1.6.0_27]
    at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:40) ~[craftbukkit_beta.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:133) ~[craftbukkit_beta.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
    ... 14 more