Support geo-traits #242
Description
Currently, the proj crates use its own Coord trait, but I'm wondering if it's possible to use geo_traits::CoordTrait instead. Considering the geo-traits crate is getting supported more and more crates, it would be easier to provide the interoperability with it rather than using the own trait.
Also, looking at georust/geo#1287 (comment), it seems geo-types will never supports 3D in order to keep backward compatibility and recommends geo-traits for 3D. So, if the proj crate wants to support 3D, probably using geo-traits is a nice idea.