Call vt.query async
Merge branch 'master' into vtquery-async
Use updated vt-query-async dep.
Use Github URL to node-mapnik

https://github.com/mapbox/carmen/issues/147
use mapnik 3.0
use 1.x release
bump mapnik
use mapnik 1.4.16+
Merge pull request #156 from mapbox/vtquery-async

Bump node-mapnik version