Update for Bungee and new 1.7.2 ping json. Also make file server-neutral.

Uses the new 1.7.2 ping format (thanks to @barneygale for the code, taken from here: https://gist.github.com/barneygale/1209061). Fixes issue with servers running behind a bungee proxy, shows correct per-server playercount. 

Also, renamed 'nerd_nu' to 'serverlist', as nerd isn't the only server using this code at this point.

Thanks.