New test result:
On windows:
This json module performance a bit slower than cjson when processing booleans nulls strings. but much faster than cjson when processing numbers.
On Linux (tested on Travis).
This json only module only a bit faster when encoding numbers.
"Ordered keys" means when this module encoding lua table as object.
Keys are sorted. But this is not true for the current developing version.
A `option.sort_keys` has added and default to false.
"detect for table types"
This json module support meta table field __jsontype to specify `"array"` or `"object"` types.
