specl: return non-zero exit status when there are failing specs.
specl: return non-zero exit status when there are failing specs.

* src/specl.lua (run): Return false when there are failing tests.

Signed-off-by: Gary V. Vaughan <f9023000f29773649f3850298becb9544b5fd6a9@gnu.org>

gvvaughan/specl