fix deprecation notices about using formats in rails 3

Change-Id: I80b8482d543ec303517dd43fc6c0a6404699326f
Reviewed-on: https://gerrit.instructure.com/30154
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jon Willesen <jonw@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>