Added some notes about API conformance
Added some notes about API conformance

mapzen/TileStache,Billups/TileStache,TileStache/TileStache,moskvax/TileStache,MetGIS/TileStache,mapzen/TileStache,SEL-Columbia/TileStache,Blechhirn/TileStache,mapzen/TileStache,jbants/TileStache,Billups/TileStache,MetGIS/TileStache,jbants/TileStache,TileStache/TileStache,SEL-Columbia/TileStache,Kosta-Github/TileStache,Kosta-Github/TileStache,moskvax/TileStache,jbants/TileStache,Blechhirn/TileStache,MetGIS/TileStache,Billups/TileStache,moskvax/TileStache,Kosta-Github/TileStache,Blechhirn/TileStache,SEL-Columbia/TileStache,TileStache/TileStache