specs: explicitly require JSON

fixes CNVS-16777

rails autoloading doesn't always work in gem-engines, I haven't tracked
down the root of the behavior, but I found a lot more explicit requires
necessary in analytics as well.

Change-Id: I780d2176dc4e1da12687b217806069647d2d31b7
Reviewed-on: https://gerrit.instructure.com/44255
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Jacob Fugal <jacob@instructure.com>
QA-Review: Jacob Fugal <jacob@instructure.com>