This test module is intended to simplify testing of external commands.
It does so by running the command under IPC::Open3, closing the stdin
immediately, and reading everything from the command's stdout and
stderr. It then makes the output available to be tested.

It is not (yet?) as feature-rich as Test::Cmd, but I think the interface
to this is much simpler. Tests also plug directly into the Test::Builder
framework, which plays nice with Test::More.

As compared to Test::Command, this module is simpler, relying on the
user to feed rc, stdout, and stderr to the appropriate other tests,
presumably in Test::More, but not necessarily.
