also pins all migrations to Rails 4.2 semantics
Change-Id: I386566f7a1f3e3e8aa31675f467c87c443457aee
Reviewed-on: https://gerrit.instructure.com/95571
Reviewed-by: Simon Williams <simon@instructure.com>
Tested-by: Simon Williams <simon@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>