restrict creationix package version

After doing steps from readme

> Install the npmpackages: npm install
> Start the server: node server/server.js
> Enjoy your local blog clone at http://localhost:8080

i got the following error (as a result of `node server/server.js`)

```js
module.js:340
    throw err;
          ^
Error: Cannot find module 'creationix'
    at Function.Module._resolveFilename (module.js:338:15)
    at Function.Module._load (module.js:280:25)
    at Module.require (module.js:362:17)
    at require (module.js:378:17)
    at Object.<anonymous> (/mnt/data/home/oleg/work/repository/git-hub/howtonode.org/server/server.js:3:18)
    at Module._compile (module.js:449:26)
    at Object.Module._extensions..js (module.js:467:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Module.runMain (module.js:492:10)
```

seems like creationix 0.4.0 is broken, so i just installed previous version (0.3.1) and it works fine