temporarily reduce build matrix to node@8
temporarily reduce build matrix to node@8

naturalatlas/node-gdal,nbuchanan/node-gdal,jdesboeufs/node-gdal,nbuchanan/node-gdal,naturalatlas/node-gdal,nbuchanan/node-gdal,jdesboeufs/node-gdal,jdesboeufs/node-gdal,naturalatlas/node-gdal,naturalatlas/node-gdal,nbuchanan/node-gdal,jdesboeufs/node-gdal