RunTests preserve status from command failures

This is the fix to travis `RunTest` failure vs success confusion.

You may pull this at your convenience.

The addition of the glf1 function to `scorer.cc` refused to be closed unless I back it out since I didn't open a separate branch for it and I really need it because `--link logistic` doesn't give correct results on [-1, 1] labels.  I changed the function name to something more correct/acceptable.  Hope it is more palatable to you now.