Add QueryMany

Ref: https://github.com/mapnik/node-mapnik/pull/292

@springmeyer [everything is passing](https://travis-ci.org/mapnik/node-mapnik/builds/32487987) except for `	linux	0.10 CXX11=true` which is the same issue as on [master](https://travis-ci.org/mapnik/node-mapnik/builds/31867628).