Fix log levels for Travis CI runs

Often we faced the error `The job exceeded the maximum log length, and has been terminated.` by Travis CI builds and then changed `./src/test/resources/log4j.properties` to a lower logging verbosity.

This also changes the verbosity for local unit test runs where verbosity isn't a problem and it's even sometimes harder to locally trace problems.

I suggest we update `./src/test/resources/log4j.properties` to a very high default verbosity level (maybe even TRACE for `io.debezium`) and then we should update `.travis.yml` to use proper log verbosity for Travis CI builds to avoid that maximum log length exceeded error by Travis CI.