Consider using new tilelive interface

[nyurik]

Hi, I am thinking of refreshing tilelive API with a new function that allows a more generic, Promise based way of requesting data: Promise<object> getAsync(object). I posted my thoughts in mapbox/tilelive#189 and an implementation that would allow to use all the older components with the new interface, or newer ones with the old one in https://github.com/kartotherian/tilelive-promise

[mojodna]

I've made some comments in the tilelive issue w/ some of my opinions.

In short, though, what's the benefit of changing?

[nyurik]

Thanks! First, this is not a change, but rather enhancement - people can continue using the existing interface. The benefits:

• ability to pass additional parameters through the stack callchain. E.g. language, licencekey, ...
• ability to handle non-tile requests like snapshots (custom area of the map with the given width/height)
• ability to integrate related services using the same pipeline (basically treating tilelive as a generic dependency container) - for example in Wikipedia, Kartotherian can get geojson for a specific area, and that same geojson could be used as an extra layer in the snapshot service. Another example - simple-style markers (pushpins) - you set marker, color, icon size, and scaling, and get back an image.