fix for rails security advisory CVE-2016-6316
fix for rails security advisory CVE-2016-6316

have to backport for rails 4.0

Change-Id: I3eef6b53bbbd5791109af28e8f8c5467332c7d22
Reviewed-on: https://gerrit.instructure.com/87527
Tested-by: Jenkins
Reviewed-by: Simon Williams <088e16a1019277b15d58faf0541e11910eb756f6@instructure.com>
Product-Review: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>
QA-Review: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>

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