force preview to 256x256 tile dimension
Copied in mostly-working VecTiles code.
Added documentation for VecTiles.
Adapted mostly-working VecTiles server code from HighRoad GeoJSON provider
Removed mapnik requirement from VecTiles geojson module
Moved VecTiles Datasource into new client submodule
Added queries parameter to VecTiles Provider
Documented most of VecTiles
Fixing Travis CI bugs
Merge pull request #108 from bwg/retinapreview

Force modestmaps preview to 256x256 tile dimensions
Added sort_key parameter to VecTiles Datasource
Bumped to 1.46.0 with addition of TileStache.Goodies.VecTiles and Sandwich patch from Lars Ahlzen