4.0.0

Breaking Changes:

• Upgrade to Elm 0.18. Thanks @stil4m for this upgrade.

Additions:

• allDifferent : List comparable -> Bool, indicate if list has duplicate values. Thanks @skitoo for this addition.
• allDifferentBy : (a -> comparable) -> List a -> Bool, indicate if list has duplicate values when supplied function are applyed on each values. Thanks @skitoo for this addition.
• groupsOfVarying : List Int -> List a -> List (List a), Thanks @patrickdet for this addition.
• stableSortWith : (a -> a -> Basics.Order) -> List a -> List a, Similar to List.sortWith, but is guaranteed to be a stable sort. Thanks @z5h for this addition.
• swapAt : Int -> Int -> List a -> Maybe.Maybe (List a), swap two values in a list by index. Thanks @roSievers for this addition.