Removed author tag inside channel tag in RSS

closes #2114
- instead of putting author in feedOptions of node-rss, it was moved to itemOptions
- supplying author: user ? user.name : null in itemOptions will still result to creating a dc:creator tag inside item tags so the info needed to have the author is still there like before
- node-rss should however still fix to not have that nasty author tag in channel tag when you supply author in feedOptions