Add support for Vagrant boxes

Hello,

I've added support for Vagrant and Chef. This will allow more automated setups (for collaborators, users and even when if they are deploying in their custom servers) and less worries about infrastructure.

I'm running right now a vagrant box on my machine and everything works just fine. 
You can take a look on the `Vagrantfile` to make sure everything is OK.

I also did a small change on the `database.sample.yml`, just to make things easier to configure or change.

I wrote a new Wiki page with instructions: https://github.com/danielweinmann/catarse/wiki/%5BEnglish%5D-How-to-install-and-run-Catarse

If you have any questions, please let me know. 

Screen#1 with the Vagrant Box Running:
![Screen Shot 2013-02-20 at 3 17 42 AM](https://f.cloud.github.com/assets/249782/174715/511d9a90-7b25-11e2-9a4f-c3814f5c9533.png)

Screen#2 with the fully functional catarse on my firefox tab after `rake db:migrate && rake db:seed`:

![Screen Shot 2013-02-20 at 3 23 16 AM](https://f.cloud.github.com/assets/249782/174726/09d2abc0-7b26-11e2-91ef-ce5acb67bc81.png)