spec: replace 'should contain' with 'should include' for rails3

Change-Id: Ia77561c179febe5a1bb78576e63151d2dbc09ffe
Reviewed-on: https://gerrit.instructure.com/30115
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>
QA-Review: James Williams  <jamesw@instructure.com>