upgrade rails 3 gem for security fixes

Change-Id: I924299bc97d11e8e03623300e4310e156bd96d16
Reviewed-on: https://gerrit.instructure.com/30822
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: James Williams  <jamesw@instructure.com>
Reviewed-by: Brian Palmer <brianp@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>