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
Sketch of using workers for the doc processing portion of indexing.
Merge branch 'auto-zxy' into index-workers

Conflicts:
	lib/index.js
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
0.8.0
Merge branch 'master' into index-workers
allow _zxy pass through
allow _zxy pass through
pass zoom through workers
Merge branch 'index-workers' into auto-zxy