code: function slugify(s, opts) {
    opts = opts || {};
    s = str(s);
    if (!opts.mixedCase) { s = s.toLowerCase(); }
    return s
      .replace(/&/g, '-and-')
      .replace(/\+/g, '-plus-')
      .replace((opts.allow ?
        new RegExp('[^-.a-zA-Z0-9' + _.escapeRegExp(opts.allow) + ']+', 'g') :
        /[^-.a-zA-Z0-9]+/g), '-')
      .replace(/--+/g, '-')
      .replace(/^-(.)/, '$1')
      .replace(/(.)-$/, '$1');
  }
docs: convert names to slugified url strings containing only - . a-z 0-9 opts.noprefix => remove leading numbers opts.mixedCase => don't lowercase opts.allow => string of additional characters to allow