Backend function now only gets called on init hook.

A small fix to prevent the plugin from being loaded too early.
It was giving errors:

Notice: Use of undefined constant TEMPLATEPATH - assumed 'TEMPLATEPATH' in /wp-includes/theme.php on line 131
Notice: Use of undefined constant STYLESHEETPATH - assumed 'STYLESHEETPATH' in /wp-includes/theme.php on line 131
Not sure why anyone would ever call this function on their own so I'd let them deal with its consequences :)