move requires usage to extension

[KristofferC]

The requires usage in this package has been profiled to cause some overhead. This moves this to extensions to avoid the overhead on 1.9:

1.8:

julia> using JSON, RecipesBase, SentinelArrays, StructTypes

julia> @time using CategoricalArrays # runs the `@require` blocks
  0.604061 seconds (1.06 M allocations: 63.916 MiB, 88.10% compilation time: 67% of which was recompilation)

1.9:

julia> using JSON, RecipesBase, SentinelArrays, StructTypes

julia> @time using CategoricalArrays # loads the extensions
  0.059438 seconds (299.68 k allocations: 21.276 MiB, 4.53% compilation time)

[vtjnash]

bump?

[KristofferC]

@andreasnoack, could we get a new release with this?

[andreasnoack]

Have there been unintended consequences of these upgraded or can I just make it a patch release?

[KristofferC]

Should be fine with a patch.