Utilities updates

Allows the helper methods that perform system calls to be stubbed for
all specs in the spec_helper.
initial vagrant box setup
add root path option to Archive (closes #300)
allow logger warnings to be ignored
establish exit status codes (closes #422)

When performing triggers:
  exit 0: all triggers succeeded without warnings
  exit 1: all triggers succeeded, but some had warnings
  exit 2: all triggers processed, but some failed
  exit 3: a fatal exception caused backup to exit

When `--check` is used:
  exit 0: success
  exit 1: failure