shims for running rails 2 with a rails 3 cache

 * cache entries are wrapped in rails 3
 * serialized attributes are handled differently
 * stub out a bunch of classes that will just be ignored
   on the returned object

Change-Id: Iff15a0f5c39cd7ceae25144585539acbfc7a62ad
Reviewed-on: https://gerrit.instructure.com/31717
Reviewed-by: James Williams  <jamesw@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>