Add slf4j-log4j12 as runtime dependency

This dependency previously existed before maven3 migration. It is needed
because, as we have transitive dependencies that rely on slf4j, we need to
provide a slf4j binding
Upgrade junit to 4.11

junit 4.10 contained an old version of hamcrest, this could lead to issue
in transitive dependency resolution issue. Now, junit 4.11 declares hamcrest
dependency.