spec: smoke test to make sure theme index renders cards
spec: smoke test to make sure theme index renders cards

closes: CNVS-29908

while QA'ing clay's react upgrade commit, it was
found that the cards on this page did not render
and it wasn't caught by jenkins. that page has a 
bunch of test coverage in jsx tests, here is 
a smoke test that it all gets put together on
a real page load

test plan:
* specs should pass
* if we break this page again in a react upgrade
  we should catch it ;)

Change-Id: I9317d0816bb8833a07c5afa088c6bcb0ac7dd937
Reviewed-on: https://gerrit.instructure.com/82229
Reviewed-by: Clay Diffrient <9dff2e5c98626d20d2848250c411e8009465bb87@instructure.com>
Tested-by: Jenkins
Product-Review: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>
QA-Review: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>

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