- Make encode/decode routines OS thread safe (within the same lua_State)
  - Optionally create an object for settings. Clone function.

- Explain limitations of using JSON as a serialisation format under Lua:
  - Tables keys:
    - Must only be integer or string
    - Integer keys will be deserialised as a string
  - Metamethods are not used when encoding tables:
    - next() is used to iterate over hashes.
    - rawget() is used when iterating over arrays.