fix incomplete result for large data

[qiao]

In your original code, the callback is called as soon as the data event is emitted.

pyg.stdout.on('data', function(data) {
  callback(data.toString());
});

This works only when the size output is small. For large output, the data event will be emitted multiple times and each time there's a partial chunk arriving. Therefore, your original approach will produce incomplete result.

[pksunkara]

Thanks man, Do you want me to publish this?

[qiao]

Yes, I have two projects depending on this module :)

[pksunkara]

Done. :)