Php options

With this PR, you can pass options to the php command. For instance, you can pass "-S 127.0.0.1:8000" and starting a new Web Server.

```php
<?php
<<<CONFIG
packages:
    - silex/silex
php-options:
    - "-S"
    - "localhost:8000"
CONFIG;
$app = new Silex\Application();
$app->get('/hello/{name}', function ($name) use ($app) {
    return 'Hello '.$app->escape($name);
});
$app->run();
```

You can test it with `melody run b217329b2c349c460b74 -vvv`
it should also work with "-d memory_limit=42M" as just one option, right?