CURATOR-139 Add slf4j-log4j test bindings

Add test bindings so that log output is preserved. Makes it easier to
debug jenkins and failed unit tests, which not appreciably increasing
the time to run or disk space used.

This closes #36
CURATOR-141 Don't make calls to the client after PathChildrenCache has been closed.

The test case is a bit weird because it needed to intercept logging.
Also, I've added slf4j-log4j12 as a test dependency to control logging.
I think it should be added to the other poms as well, otherwise logging
seems to get lost.
CURATOR-141 Changed the way we detect a working log setup
Merge branch 'CURATOR-141' of https://github.com/karel1980/curator into CURATOR-141
CURATOR-141 - Reverted the logging additions to the pom.xml as they have already been covered by CURATOR-139