GROOVY-6424: @GrabExclude's group element is documented as optional but the implementation requires it
GROOVY-6424: @GrabExclude's group element is documented as optional but the implementation requires it

improved the javadoc and added some tests
Merge pull request #286 from PascalSchumacher/GROOVY-6424

GROOVY-6424: @GrabExclude's group element is documented as optional but ...