made composer friendly

I've made this library composer friendly, now someone can install it in their app by doing something like

```json
"repositories": [
        {
            "type": "vcs",
            "url": "https://github.com/regru/php-whois"
        }
    ],
 "require": {
        "phois/whois":                   "dev-master"
    },
```

```bash
composer install
```

I've also renamed the class and some of the functions to make the more object oriented-y 
e.g.
is_available -> isAvailable 

and also updated the examples.