beautify does not work; should be an output option

[josephg]

$ npx browserify -t [ uglifyify -b ] a.js 
DefaultsError: `beautify` is not a supported option while parsing file: a.js

The problem is this code:

  if (opts.b) {
    opts.beautify = opts.b
    delete opts.b
  }

... Should instead be setting beautify in opts.output:

  if (opts.b) {
    if (!opts.output) opts.output = {}
    opts.output.beautify = opts.b
  }