CI: store logs (#1596)

We have a flaky spec that would be easier to debug if they were
available.

Author: mockdeep

.circleci/config.yml

@@ -143,3 +143,7 @@ jobs:
       - store_artifacts:
           path: tmp/capybara
           destination: capybara
+
+      - store_artifacts:
+          path: log
+          destination: log