don't allow ruby 2.2 with rails 3

Change-Id: I0544ad72d48ace97a1c9ba85f34ee4a961d4460d
Reviewed-on: https://gerrit.instructure.com/46325
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Rob Orton <rob@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>