allow rails 3 style "don't validate" options to ActiveRecord::Base#save

Change-Id: Ice8121bce49982641b4f30d01fa31f2a1722bac7
Reviewed-on: https://gerrit.instructure.com/28713
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: James Williams  <jamesw@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>