install iconv, drop iojs builds
install iconv, drop iojs builds

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