minor, provide -k|--keep-going

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
test, provide regressions for the keep-going feature

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'feat/keep-going'

* feat/keep-going:
  test, provide regressions for the keep-going feature
  minor, provide -k|--keep-going
minor, provide expect/negate clauses (operators ? and !)

The failure of the command after ! is considered a success, if the command
succeeds it is considered a failure.
For fine-grain control ?n allows to only accept return code N as successful.

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
test, provide regressions for the expect/negate operators

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'feat/negexp'

* feat/negexp:
  test, provide regressions for the expect/negate operators
  minor, provide expect/negate clauses (operators ? and !)
doc, explain ignore, negate, and expect operators by example in README.me

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>