GeometryCollection support

[ilyashuma]

I ran into a need to use contains?/2 with a GeometryCollection as an argument. There is no support for complex geometries, so I implemented a helper to flatten GeometryCollection into non-complex MultiPolygon geometry.

I'm wondering if there is a place in topo for this feature? I'd be happy to contribute.

[pkinney]

There's a PR open (#13), but it needs tests and to be extended to the other functions. If you're up for adding to that, feel free.

Either way, you're not the first person to ask for it, so I will add it to the backlog.

Thanks

[ilyashuma]

Thanks for the answer, Powell! I'll spend some time working on this.