Bug with directory location in the server.js file in the Book Library app

Hello Addy.

This is my first issue on GitHub, I hope I'm doing this right, but let me know if I need to make a pull request for this. I would be happy to. Thank you for the Backbone Application book. It's been great to work through so far, and I appreciate your thorough explanations.

Ok, when I typed out your code for the `server.js` file in my application, I got an error in the window: `Cannot GET /` . Also in the dev tools, `http://localhost:4711/` returns a `404 Not Found`.

I think the issue is with the line of code in `server.js`:
`app.use( express.static( path.join( application_root,'../', 'site') ) );`

This moves the reference out of the root folder, as I understand it. When I took out the two `..`, the app displays fine, so now, my line of code looks like:
`app.use( express.static( path.join( application_root,'/', 'site') ) );`

This is assuming that the `server.js` file is running in the root at the same level as the `node_modules` and `site` directories, which is what I understood from your directions.

I think I'm supposed to submit a PR for this, which will also be my first. Please let me know if I'm getting this right, or what you would like me to do from here.

Again, thanks!
Nate