Add log4j example.

Hi mr. Seeberger,
I must apologize for new Pull request, but I am still confused from git (sweet SVN for me :-) ).I have still problem with collapse commits into one. I need probably some advice.

Please forgot my first pull request.

I hope that mine last commit (still not one) will be ok. 

I am not sure with this line:
libraryDependencies ++= Seq(Dependencies.Test.log4jCore),
but in mine opinion this way is right, because log4jCore dependency is used only in scalalogging-log4j-test project.

I will write similar example for slf4j logging ok?

again, sorry for inconvenience.
JuBu