Fellow WordPress developers building websites, I beg you. Please learn about must-use plugins, and every time you think about adding a special hook to your functions.php file, think for a moment - is what you're adding going likely going to want to continue to be used when you change themes? If so, put it in your must-use plugin instead of the theme. You'll save yourself (or the next person to work on this site) so many headaches when you change the theme in the future.