src/index.js
function rot13(str) {
  return str.replace(/[a-zA-Z]/g , function(c) {
    return String.fromCharCode(
      (c <= 'Z' ? 90 : 122) >= (c = c.charCodeAt(0) + 13 ) ? c : c - 26);
  });
}
function rot13(str) {
  return str.replace(/[a-zA-Z]/g , function(c) {
    return String.fromCharCode(
      (c <= 'Z' ? 90 : 122) >= (c = c.charCodeAt(0) + 13 ) ? c : c - 26);
  });
}
Performs rot13 encoding/decoding
@param  {String} str
@return {String}