Add compatibility with Spigot 1.7.10 - 1.8 Protocol hack.

Thanks to @Minecrell and @kashike for discovering an equivalent fix 
in Spigot. See issue #60. :)
Distinguish this Spigot 1.8 compatible build in plugin.yml.

Change "SNAPSHOT" to "HACK" to indicate that this is a temporary 
snapshot build that is compatible with Spigot's Protocol Hack. We 
don't really intend to release this on BukkitDev. 

See #60.