Added support for custom Configuration.index
Added support for custom Configuration.index

mpuig/TileStache,Billups/TileStache,moskvax/TileStache,SEL-Columbia/TileStache,jbants/TileStache,jbants/TileStache,moskvax/TileStache,moskvax/TileStache,Billups/TileStache,SEL-Columbia/TileStache,Blechhirn/TileStache,MetGIS/TileStache,MetGIS/TileStache,robpvn/Vector-Tile-Research,Blechhirn/TileStache,Kosta-Github/TileStache,mapzen/TileStache,Billups/TileStache,mpuig/TileStache,Kosta-Github/TileStache,TileStache/TileStache,mapzen/TileStache,SEL-Columbia/TileStache,Blechhirn/TileStache,mapzen/TileStache,TileStache/TileStache,robpvn/Vector-Tile-Research,jbants/TileStache,MetGIS/TileStache,Kosta-Github/TileStache,mojodna/TileStache,TileStache/TileStache,mojodna/TileStache,robpvn/Vector-Tile-Research