notifications improvement, now we make sure that the username has passed through...

notifications improvement, now we make sure that the username has passed through the smart_unicode function and the returned object is a safe unicode string. This used to cause some trouble with the new comment posted notifications. Also fixing a small bug in the accepted answer notifications. The Question object shouldn't go through the smart_str function, then the Question object gets converted to a Unicode string and this caused trouble with the URL reverse process.

git-svn-id: http://svn.osqa.net/svnroot/osqa/trunk@985 0cfe37f9-358a-4d5e-be75-b63607b5c754