function prefixToArray(prefix) {
  var result = [];
  for (var i = 0; i < prefix.length; i++) {
    result.push(prefix.charCodeAt(i) & 31);
  }
  return result;
}
Derives an array from the given prefix to be used in the computation
of the address' checksum.

@param {string} prefix Network prefix. E.g.: 'bitcoincash'.