delta/detailed.tests#t3 -- exit status test

delta should have similar exit statuses as standard UNIX diff. When there is
a difference between the --from graph and the --to graph, delta should exit
with status 1. If there are no differences, delta should exit with status 0.

issue originally raised in the following bug:
http://lists.w3.org/Archives/Public/public-cwm-bugs/2005Feb/0000

options passed to cwm:
delta/t3/test.n3 --think --with `../delta.py -f delta/t3/from.n3 -t delta/t3/to-same.n3 &> /dev/null; echo $?` `../delta.py -f delta/t3/from.n3 -t delta/t3/to-diff.n3 &> /dev/null; echo $?`

reference output:
delta/t3/output.n3