Bukkit

What steps will reproduce the problem?
1. Run arena railgun 0.5 on 1.7.10 server
2. console error at startup
3. Plugin dont run

What is the expected output? What do you see instead?
[01:34:17] [Server thread/ERROR]: Could not load 'plugins/ArenaRailgun.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.NoClassDefFoundError: net/minecraft/server/v1_7_R3/Packet
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:133) ~[spigot.jar:git-Spigot-1604]
    at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:329) ~[spigot.jar:git-Spigot-1604]
    at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:251) [spigot.jar:git-Spigot-1604]
    at org.bukkit.craftbukkit.v1_7_R4.CraftServer.loadPlugins(CraftServer.java:369) [spigot.jar:git-Spigot-1604]
    at net.minecraft.server.v1_7_R4.DedicatedServer.init(DedicatedServer.java:152) [spigot.jar:git-Spigot-1604]
    at net.minecraft.server.v1_7_R4.MinecraftServer.run(MinecraftServer.java:458) [spigot.jar:git-Spigot-1604]
    at net.minecraft.server.v1_7_R4.ThreadServerApplication.run(SourceFile:628) [spigot.jar:git-Spigot-1604]
Caused by: java.lang.NoClassDefFoundError: net/minecraft/server/v1_7_R3/Packet
    at java.lang.Class.forName0(Native Method) ~[?:1.7.0_55]
    at java.lang.Class.forName(Class.java:270) ~[?:1.7.0_55]
    at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:64) ~[spigot.jar:git-Spigot-1604]
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:129) ~[spigot.jar:git-Spigot-1604]
    ... 6 more
Caused by: java.lang.ClassNotFoundException: net.minecraft.server.v1_7_R3.Packet
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:91) ~[spigot.jar:git-Spigot-1604]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:86) ~[spigot.jar:git-Spigot-1604]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:425) ~[?:1.7.0_55]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:358) ~[?:1.7.0_55]
    at java.lang.Class.forName0(Native Method) ~[?:1.7.0_55]
    at java.lang.Class.forName(Class.java:270) ~[?:1.7.0_55]
    at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:64) ~[spigot.jar:git-Spigot-1604]
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:129) ~[spigot.jar:git-Spigot-1604]
    ... 6 more

What version of the product are you using?
0.5

Do you have an error log of what happened?
see up

Please provide any additional information below.
Dont work. and i need it for create quake arenas!