Better handling of self-listens

[sudara]

I'd like to encourage the ability to self-listen without affecting play count or placement on kicking ass, while simultaneously maintaining an accurate counters of number of plays for admin/mod/stats.

1. Have another counter on asset called self_listens_count
2. On listen, if it's same IP or account, don't increment listens_count
3. On asset#show, don't display own user in "latest listeners"
4. In kicking ass algo, remove penalty for self-listens and rely only on listens_count