enable debugging in rails 3 specs without '-d' option

Change-Id: I898645bb63d1bb76f888cbf23fe867d6d71c7229
Reviewed-on: https://gerrit.instructure.com/30018
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>
QA-Review: James Williams  <jamesw@instructure.com>