Addresses issue #1463. Replaces preg_replace '\e' modifier with preg_replace_callback as '\e' is depracated as of PHP 5.5.0.
Merge branch 'master' of https://github.com/danielnr/YOURLS into danielnr-master
Remove /e in preg_replace. Fixes #1463

This is just a quick fix. This will be replaced in 2.0 with function yourls_replace_string_tokens() from the Feature-Design branch