Drop optional dependency

[ParadaCarleton]

The single line:

setindex(a::StaticArrays.StaticArray, args...) =
            Base.setindex(a, args...)

Makes up most of the package's compile time; it could easily be moved to StaticArrays.jl, avoiding the cost of having to use Requires.jl.

[jw3126]

I would love to drop this, but it is not as easy as you think. It would require a change in base, see JuliaLang/julia#33495
If you want this, it would be awesome if you could revive that Base PR.

[jw3126]

mostly solved by #174