Add slf4j to test dependencies
Add slf4j to test dependencies

Co-authored-by: Ignasi Marimon-Clos <4c0bd14b7e09a49d1038f1ff6661645915f8d416@lightbend.com>

ignasi35/lagom,TimMoore/lagom,ignasi35/lagom,TimMoore/lagom,ignasi35/lagom,TimMoore/lagom,ignasi35/lagom,lagom/lagom,lagom/lagom,rcavalcanti/lagom,ignasi35/lagom,rcavalcanti/lagom,lagom/lagom,TimMoore/lagom,lagom/lagom,lagom/lagom,rcavalcanti/lagom,rcavalcanti/lagom,TimMoore/lagom