Capability check prevents use in non-authenticated contexts

[chrisvanpatten]

The capability check inside wp_set_terms_for_user prevents you from using the function in a non-authenticated context, such as inside a cron event.

I think this function should actually be split into wp_bulk_set_terms_for_user which provides the specific bulk functionality, and wp_set_terms_for_user which is a simpler wrapper around wp_*_object_terms.

This would also make it easier to solve #19 and possibly #18 too.

[JJJ]

21 is merged, so this is taken care of. Thanks @chrisvanpatten!