Dangerous pirate of `fill` function

It breaks down my code when I add it to my dependency, this turns out to be the cause.

```julia
julia> fill([])
0-dimensional Array{Vector{Any}, 0}:
[]

julia> using Compose

julia> fill([])
Compose.Property{Compose.FillPrimitive}(Compose.FillPrimitive[])
```

Maybe we should not pirate the `fill` function?