streaming JSON.parse and stringify

 JSONStream.parse(pattern, map) provide a function that can be used to map or
 filter the json output. map is passed the value at that node of the pattern,
 if map return non-nullish (anything but null or undefined) that value will be
 emitted in the stream. If it returns a nullish value, nothing will be emitted.
 .
 JSONStream also emits 'header' and 'footer' events, the 'header' event
 contains anything in the output that was before the first match, and the
 'footer', is anything after the last match.