Slow no longer stack; Frozen Mallet seems obsolete

• Slow no longer stack, only the strongest slow applys (patch 5.13)
• Movement Speed stack
• The Black Cleaver is cheaper than Frozen Mallet and has better stat

I now feel like that Frozen Mallet is no longer useful on the game, and it seems like noob trap to me.

Champion that doesn't have instant gap-closing, may already have slow ability (such as Nasus, Olaf).

I think it's good idea to completely remove/rework this item.