sendFile (capital 'F') requires

Just replacing "sendfile" with "sendFile" results in "TypeError: path must be absolute or specify root to res.sendFile". I think specifying an absolute path utilizing the __dirname Node.js global is best, rather than introducing the options object for sendFile.
http://nodejs.org/docs/latest/api/globals.html#globals_dirname
http://expressjs.com/api.html#res.sendFile