Added spigot events and handler

From https://github.com/SpigotMC/Spigot-API/tree/master/src/main/java/org/spigotmc
This adds Spigot's additions to the Bukkit API that are easily tracked. More additions may be available in org.bukkit but we'll have to add those later after a discussion on what we should add from there. (partially 'fixes' #18)

Thanks to the Spigot team for supplying this extra stuff!