Selectors don't change
Things happen in less than a second
Remove an extra empty line
Wrap code in an interval, check for active mail_body

This fixes #17. On the way to fixing it, I notice 
a bug with flipping between mails using < and > or
last and next page button/shortcut.e We need to find 
link AFTER the next content is added to the DOM, 
check for the right mail_body, and then query the
links within that mail_body; otherwise, the links
from the previous mail_body will get appended.
Clear all the intervals
Merge pull request #18 from muan/muan/fix-things

Fix things