function decode(base32) {
  $.checkArgument(typeof base32 === 'string', 'Must be base32-encoded string');
  var data = [];
  for (var i=0; i<base32.length; i++) {
    var value = base32[i];
    $.checkArgument(value in CHARSET_INVERSE_INDEX, 'value '+ value);
    data.push(CHARSET_INVERSE_INDEX[value]);
  }
  return data;
}
Decodes the given base32-encoded string into an array of 5-bit integers.

@param {string} base32