TODO: sf version of points_elided

[hrbrmstr]

With the addition of points_elided() by @rdinter prbly shld add support for it in the sf world.

Also add @rdinter to the DESCRIPTION and Rd author field

[rdinter]

I'll take a look at the sf package and adapt what I did from the rd3albers repository to the one here, support for a different class might be a bit over my head right now but that'll be good experience. It'll put hair on my chest, so to speak.