Only show cider-test-report buffer on test failures

[r0man]

I think popping up the *cider-test-report* is only useful if
tests have actually failed. Most of the time I immedialtly close
that buffer again if tests were passing, and I think the
notification in the message buffer is enough.

If there is interest for this I can prepare a patch ...

Roman

[bbatsov]

Currently - yes. But if we display more information about the tests that were executed (which we'll probably do at some time) it might be more useful even for passing tests.

That said, I'm ok with making this configurable if @jeffvalk is ok as well.

[ikbrunel]

Seconded!

[bbatsov]

Fixed in #743.