[pom] Update slf4j to 1.8.0-beta4
[pom] Update slf4j to 1.8.0-beta4

hazendaz/waffle,Waffle/waffle,Waffle/waffle,dblock/waffle,hazendaz/waffle,dblock/waffle,hazendaz/waffle,dblock/waffle,dblock/waffle,Waffle/waffle