Update README.md to use GeometryOps

[asinghvi17]

Leads to a simpler API for the buffer (though the result is still a planar buffer and not spherical, so will be quite distorted)

[tiemvanderdeure]

I didn't know GeometryOps had a convex hull method, thanks!

Now that we can specify Planar or Spherical geometry I might look into writing a spherical buffer method :)

[asinghvi17]

I just read a paper about this...will track it down and send it to you! Spherical buffer would be great because s2's version is actually pixelated, lol

[rafaqz]

We don't have native Planar buffers either, its just calling LibGEOS. You could do both! ;)