Use vector-tile for geometry/property handling

[mapsam]

@flippmoke has been working on a new version of lib vector-tile over at https://github.com/mapbox/vector-tile/tree/2.x - let's start using some of the helpful methods there!

[springmeyer]

👍 for geometry handling. For property handling however, like shaver, I'm less certain that the generic solution that we currently offer in mapbox/vector-tile will be appropriate. (and I've mentioned this to @flippmoke). The issue I see is that mapbox/vector-tile will use the property_map type from mapbox::geometry::feature (or mapbox::feature if you use mapbox/geometry.hpp#52). And this property_map is a std::map. And unless you need to search it frequently std::map is a less efficient choice because it is more expensive to create than std::vector<std::pair<key_type,value_type>> per https://github.com/mapbox/vt-shaver-cpp/commit/aea952ef4a26a24e393c8022dd51599f2b170b68 and Use more appropriate container types at #30.

So, my opinion is that performance matters enough in vtzero that we should be using external deps only if they increase performance.

[mapsam]

Resolved in #42 and a major increase in perf!