Group stdout together by process

Thanks again for this library. It's pretty awesome and fulfilling a big need.

After implementing #12, the process output is extremely valuable.

I'm wondering if there is a good method of grouping this output by process (even if it means there is no output until after the process or parent process completes). As we troubleshoot / analyze the output, we find we spend some time sifting through things to see the output from each process together.

I have some hair-brained ideas that involving parsing and looping through the full output and then displaying it, but wanted to see if there were any possibilities that are "more native."

Thanks!

C