pom.xml: resolve conflicts with slf4j
pom.xml: resolve conflicts with slf4j

Downgrade version and use explicit exclusion of transitive log4j
dependency (requires 1.2.14, we want to stay at 1.2.13).

Signed-off-by: Pierre-Alexandre Meyer <ff019a5748a52b5641624af88a54a2f0e46a9fb5@ning.com>

pierre/eventtracker