Torrent as text

This adds a link to download a given torrent file as a plain text file.  Some firewalls and web filters block 'application/x-bittorrent' content types, and sending the torrent file as a text file circumvents this block.

The rewrite rules were tested with both nginx and Apache.  I've also removed the 'if' blocks from the nginx rules as they don't do anything and they are [evil according to the nginx devs](http://wiki.nginx.org/IfIsEvil).