Fix typespecs for functions taking and returning functions

[wende]

Add:

Example:

fun : (a -> b) -> (a -> b)

->

@spec fun(any -> any) :: (any -> any)

instead of

@spec fun(any) :: anyany) :: any

[wende]

It's gonna be tricky, because in Elm

a -> b -> ( c -> d) 

equals

a -> b -> c -> d

but in elixir

spec a(b) :: (c -> d)

doesn't equal

spec a(b, c) :: d)