update ember-data to 1.0.0-beta.7

Change-Id: I5660379f9fe967403824ed1065b0bdd727b03fb3
Reviewed-on: https://gerrit.instructure.com/30366
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Stanley Stuart <stanley@instructure.com>
Product-Review: Stanley Stuart <stanley@instructure.com>
QA-Review: Stanley Stuart <stanley@instructure.com>