Bumped slf4j version to 1.7.16
Bumped slf4j version to 1.7.16

There were several important fixes since the currently used 1.7.13.
Read the release notes http://www.slf4j.org/news.html for details.

playframework/playframework,Shruti9520/playframework,Shruti9520/playframework,marcospereira/playframework,hagl/playframework,wegtam/playframework,hagl/playframework,marcospereira/playframework,benmccann/playframework,rajeshpg/playframework,wsargent/playframework,richdougherty/playframework,richdougherty/playframework,Shruti9520/playframework,marcospereira/playframework,zaneli/playframework,Shenker93/playframework,Shenker93/playframework,aradchykov/playframework,ktoso/playframework,hagl/playframework,zaneli/playframework,playframework/playframework,richdougherty/playframework,zaneli/playframework,wsargent/playframework,ktoso/playframework,ktoso/playframework,benmccann/playframework,rajeshpg/playframework,zaneli/playframework,rajeshpg/playframework,wsargent/playframework,wsargent/playframework,mkurz/playframework,wegtam/playframework,benmccann/playframework,richdougherty/playframework,aradchykov/playframework,marcospereira/playframework,Shruti9520/playframework,aradchykov/playframework,wegtam/playframework,benmccann/playframework,ktoso/playframework,hagl/playframework,playframework/playframework,Shenker93/playframework,mkurz/playframework,mkurz/playframework,rajeshpg/playframework,wegtam/playframework,mkurz/playframework,aradchykov/playframework,Shenker93/playframework