Post parameters using cURL, to allow file uploads.

As the title says. The current implementation puts all parameters in the query string. By doing it through post, you can upload files, like this:

```php
$response = $fogbugz->edit(
    array(
        'ixBug' => 385,
        'File1' => '@C:\myfile.jpg',
        'nFileCount' => 1,
    )
);
```