Deprecated usage of bodyParser() and npm Invalid warning

In **Exercise 2 - Book Library application**, the usage of `bodyParser()` constructor in `server.js` has been deprecated as of **2014-06-19**.

`app.use(bodyParser()); // deprecated`

Instead of this line, it needs to be used as the following code:

```
app.use(bodyParser.urlencoded({
extended: true
}));

app.use(bodyParser.json());
```

In addition, when installing the **npm packages**, body-parser dependency is listed as `"~1.9.1"` in the `package.json` file. It will cause the **npm ERR! invalid: body-parser@1.9.3** warning when you listed your installed npm packages by the command of `npm list`.

_(Personally, I solved this warning by `npm update` command.)_

So instead of `"~1.9.1"`, it should be listed as `"~1.13.3"` (as the time of this issue writing, the latest body-parser is "1.13.3").

Thanks.