Ticket 294: Blog: next and previous don't work when blog-items has same publish_on date

Problem description forum:
http://forum.fork-cms.com/discussions/3xx/509-blog-next-and-previous-dont-work-when-blog-items-has-same-publish_on-date

Lighthouse Ticket:
http://forkcms.lighthouseapp.com/projects/61890/tickets/294-via-tender-blog-next-and-previous-dont-work-when-blog-items-has-same-publish_on-date