What could the increased number of NYPD on foot in the South Williamsburg area mean? One reader tips us off to a new South Side stabber who may have the 90th Precinct working overtime. Ladies, hipsters, et al, even though Matchbox 20 and McLovin were bro-ing down south of the Williamsburg Bridge – the ultimate sign of gentrification – you still need to buddy up on those evening walks. A tipster writes:There is a man......