Upgraded to Lua 5.2, use "reuseport" option

* lua/ar_main.lua:
  Upgraded to lua5.2; setfenv doesn't exist in >=5.2, instead you call
  `load` with an enviroment.

* luaserver.lua:
  Use the default Lua version (should be 5.2 on up to date systems)
Added `socket.bind_reuseport` so if you're using a new version of
  luasocket, you can run multipul instances (like threads) of the
  server, on the same port.
`settimeout` is currently broken due to beta luasocket (on my machine)

* inc/request.lua:
  Eh, append error for clear reason as to why it failed

* inc/util.lua:
  Whoops, forgot to call the function and return