Add test coverage for #607 (safesystem w/ no $SHELL)

Also: Add missing SecureRandom.uuid under 1.8.x (for the tests)
Upgrade arr-pm to 0.0.9; fixes a race condition in RPM file reading

This only affected the tests, best I can tell, but would have only
caused problems for using '-s rpm' (rpm input).
Goodbye, Tempfile, I hated you always.

Now uses Stud::Temporary. Much happier.
(Tempfile uses finalizers to remove files on disk during GC, which
messes things up if all you want is a temporary "path name" not a file
itself.)
typo
Use /bin/sh as the default if $SHELL isn't set in the environment.

Fixes #607