"--invert false" setting doesn't work

[rufushuang]

Is it caused by the 'optimist' doesn't support 'auto' on 'boolean' type?

    .options("invert", {
      describe: "in conjunction with --width or --height, whether to invert y",
      type: "boolean",
      default: "auto"
    })

when '--invert false' is set, the argv.invert changes to be an array insteadof a string

argv.invert == ['auto', false];

This can be reviewed as following code change to bin\topojson

      console.log("1:"); console.log(argv.invert);
      if (argv.invert.length !== undefined) argv.invert = argv.invert[argv.invert.length - 1]
      console.log("2:"); console.log(argv.invert);
      if (argv.invert === "auto") argv.invert = !argv.projection;
      console.log("3:"); console.log(argv.invert);

Add argv.invert = argv.invert[argv.invert.length - 1] can fix the 'true'/'false' setting, but it makes 'auto' setting useless.

[rufushuang]

or should we deal with the array-ed invert option in
'lib/topojson/scale.js'

12 "margin" in options && (margin = +options["margin"]),
13 "invert" in options && (invert = !!options["invert"]);

fix it in line 13 instead?

[mbostock]

The --invert functionality is moving to d3-geo-projection’s geoscale in 2.0, and I’ll be using commander instead of optimist.