"Left 4 Dead with ratmen" is how I'll crudely summarise what little I know about the newly announced Warhammer: The End Times - Vermintide [official site]. It's a co-op FPS pitting heroes against hordes of Skaven in shoot-o-melee action, coming in the second half of this year from War of the Vikings makers Fatshark.Warhammer 40K is more my bag than Warhammer Fantasy, so all I…