Fixes "cp: cannot create regular file `vendor/php/etc/conf.d': No such file or directory"

If using the extra.heroku.php-includes option, this line was pointing to the wrong destination vendor path and threw a missing file or directory error.
Merge pull request #58 from hedinfaok/patch-1

Fixes "cp: cannot create regular file `vendor/php/etc/conf.d': No such f...