Usage: mbliberator [options] mbtiles outpath
  Options:
    -h, --help               output usage information
    -V, --version            output the version number
    -p, --parallel <n>       max number of parallel writes
    -m, --mbutil [callback]  mbutil mode, also used to set the grid callback for mbutil mode, if omited defaults to "grid", set to "" to turn off jsonp