Add check_output() and tee() to the process module.
Add check_output() and tee() to the process module.

These are useful functions for capturing the output of jobs run via
subprocess.  The check_output() function is actually copied straight
from the python2.7 standard library, but it's useful on the cluster
where python2.7 isn't installed and this function isn't otherwise
available.

Kortemme-Lab/klab,Kortemme-Lab/klab,Kortemme-Lab/klab,Kortemme-Lab/klab