Allow CodeIgniter Projects to be deployed with composer

Adding a project name to CodeIgniter's composer.json file will allow the file to be submitted to Packagist:
https://packagist.org

When CodeIgniter is the main Composer repository, users will be able to deploy CodeIgniter with this simple command:

````````shell
php composer.phar create-project ellislab/codeigniter path/ 2.1.0
````````

Without the changes in this pull request, CodeIgnitor Fails the Packagist repository verification found here: https://packagist.org/packages/submit
The changes (only to a single file, composer.json), make CodeIgnitor pass the validation and the submission can take place.

I believe that, since such a simple change can add so much value and ease of use to CodeIgnitor, it should be included in the repository.

thanks!