code: function increment (vString) {
    var match = versionParse(vString);
    var a = match[1];
    var b = match[2];
    var c = match[3];
    var d = match[4];
    var lastPos = vString.length - 1;
    var lastChar = vString.charAt(lastPos);
  
    if (!b) {
      return vString + (lastChar === '.' ? '' : '.') + '1';
    }
    if (!c) {
      return vString + '1';
    }
    if (!d) {
      return vString.substr(0, lastPos) + (++lastChar);
    }
    return vString.substr(0, lastPos) + String.fromCharCode(lastChar.charCodeAt(0) + 1);
  }
docs: Takes a version string ('1.2.3') and returns a version string
  that'll parse as greater than the input string by the smallest margin
  possible ('1.2.3.1').
  listed as number-A, string-B, number-C, string-D in
  Mozilla's Toolkit Format.
  https://developer.mozilla.org/en-US/docs/Toolkit_version_format
  
  @param {String} vString
  @return {String}