Improve the test reports on Travis.

It's not easy to navigate to the failed tests to see what happens.
It would be great to add functionality to navigate to failed tests or simply just print the failed logs.

It seems it is not officially supported by Travis yet.
* Ref: https://github.com/travis-ci/travis-ci/issues/439

Not sure the TestLoggingContainer plugin of Gradle fits in our case but I think it's worth digging in.
* Ref: https://docs.gradle.org/current/dsl/org.gradle.api.tasks.testing.logging.TestLoggingContainer.html

## Environment details:

* Travis