Initial work on the JSON5.stringify method

Here is my work on the stringify method.  Basic work is complete and tested.  The space argument (3rd) is partially implemented, but disabled until I can fully test.  The replacer argument (2nd) is not implemented.  I don't plan to implement this one since it seems a bit esoteric to me.

I probably have a few more hours worth of work before I can tidy up the space argument support.  But, feedback is welcome up until this point.  Thanks.