remove redundant bbox intersection clause

Postgis performs a bounding box check as part of its ST_Intersects
implementation.
http://lists.osgeo.org/pipermail/postgis-users/2010-September/027675.html
suppress simplification at particular zooms levels
specify allowed geometry types per layer

Configuring the layers in advance prevents the query from having to
perform a check to ensure that the geometry type returned is consistent.
sort by id to ensure stable results ordering
Merge pull request #16 from mapzen/performance-updates

Performance updates