rails4: upgrade redis-store and friends

fixes CNVS-15414

This applies to rails3 as well, we just use the appropriate version of
redis-rails for each.

test plan: redis should work as before, for both cache and data.

Change-Id: Ic34729190936a133b908e31ff186934fa435c1b6
Reviewed-on: https://gerrit.instructure.com/40898
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Brian Palmer <brianp@instructure.com>