[Website] Attachments with apostrophe (') breaks link

Steps to reproduce bug
1. Open the following forum topic: http://musescore.org/en/node/9148#comment-30720
2. Click on the "mags' mandolin tune.txt" attachment

Expected behavior: Attachment should download normally:
http://musescore.org/sites/musescore.org/files/mags%27%20mandolin%20tun…

Actual behavior: Website gives a "Page not found" error:
http://musescore.org/sites/musescore.org/files/mags&%23039;%20mandolin%…

Discussion: The apostrophe in the file name causes problems. "'" should be escaped to "%27".