add :context option to group spec_helper

Change-Id: Ie65a2a2b9e306fd8ec6eb47e317ad42c43db2c48
Reviewed-on: https://gerrit.instructure.com/28975
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>