Fix templating with php::conf and remove metaparameters

As proposed in the overing section of the README.md the usage scenario will be like: 

```
php::conf { 'php.ini-cli':
  path     => '/etc/php5/cli/php.ini',
  template => 'example42/php/php.ini-cli.erb',
}
```

Though the `php::conf` faild to provide a mechanism to pass parameters (values) to the template. Thus making this approach not usable (or at least not templatable)