starsha: Text on STDERR doesn't mean we failed

Text on stderr indicating failure causes us to be very fragile to a
lot of things which keep being relatively insignifcant / not really
problems.

This changes the code to just use <base/subprocess.h> directly, which
gives us what we want more concisely than getting the behavior out of
TCorpus::Run.
Merge pull request #66 from cmaloney/misc_cleanup

starsha: Text on STDERR doesn't mean we failed