Split implementations into producers and consumers

[pnorman]

https://github.com/mapbox/vector-tile-spec/wiki/Implementations could be clearer if it split apart into producers and consumers of vector tiles. Some do both, but many are just one side.

There may also be some duplication - I see more than one link which is Mapnik under the hood. Is it useful to list all libraries and applications which use mapnik-vector-tile?

[tmcw]

@pnorman the wiki is editable by anyone, right?

[pnorman]

@pnorman the wiki is editable by anyone, right?

Yes.

[tmcw]

Feel free to submit a PR to https://github.com/mapbox/awesome-vector-tiles with this change.