Birthday thread 2.5

Birthday thread v1.5 changes:

Updated thread title phrase.

Birthday thread v1.4 changes:

Added checks to ensure Options have been set.

Birthday thread v1.3 changes:

This version requires you to uninstall any previous version first.

1) Uninstall previous version of Birthday thread.
2) Delete the Andy/BirthdayThread directory on your server.
3) Install latest version.

This new version now uses the XenForo cron entry.

Birthday thread v1.2 changes:

Updated PHP code and Options page. Fixed bugs which prevented birthday thread from being created.

Birthday thread v1.1 changes:

Updated addon.json file.