scope.sh: Compatibility with `sh`

The success() function has been replaced with a POSIX-compatible one.
SIGPIPE is handled internally. Returns 0 if _all_ the commands were
executed successfuly as an addional sanity check.
The case constructs' contents have been modified accordingly.
scope.sh: success() returns index of failed command

This should allow for easier debugging.
scope.sh: bsdtar added as archive content lister
Merge branch 'master' of github.com:zmode/ranger