add support for composer

Hi,
this patch add support for pharen on composer. After install pharen with composer the code will finish in vendor/pharen  and the command pharen in vendor/bin.

this is a example of composer.json for import pharen.

```
{
    "name": "francesco/provapharen",
    "repositories": [
        {
            "type": "git",
            "url": "https://github.com/francescoagati/pharen.git"
        }
    ],
    "require": {
	"pharen/pharen": "dev-composer"
    }
}
```