TODO:
-----

 -- hiredis.unwrap_reply should pass everything through without looking
    if it is called with more than one argument,
    so this would not lose an error:
        hiredis.unwrap_reply(conn.command())
 -- Document current API.
 -- Run splint all over it.
 -- Run under valgrind
 -- Bind whole API.
 -- Write better tests.
 -- Add a luajit.ffi binding.
 -- Do not leak reply object if Lua throws error during handling.
 -- Double-check all Lua data stack manipulations.
 -- Call luaL_checkstack() where appropriate.
