Run cleanup() when test runner supports teardown()

[screendriver]

I guess my comment in my pull request #676 was overlooked but I don't know how to fix my pull request:

• linting fails because teardown is not defined. Is this somewhere deep in eslint-config-kentcdodds?
• I had problems to write a test for that because you are using Jest which does not have teardown()

[eps1lon]

Sorry for letting the PR get stale. Let's keep the discussion in the PR though.