Curl support

This will add extra functionality to the Spil Games API PHP Client

* You can now change the endpoint if you want to something else than https://api.spilgames.com, this can be used by if you have to use a proxy like _https://api.spilgames.com.local_

```php
SpilGames::set(SpilGames::SETTING_ENDPOINT, 'https://proxy.to.the.api.lcoal');
```

* You can now turn off SSL verification, this is mostly needed if the partner uses a proxy.

```php
SpilGames::set(SpilGames::SETTING_SSL_VERIFY_PEER, false);
```

* You can now also change the CA path that is used for SSL verification. This can be path to an directory or to an file. default is 

```php
SpilGames::set(SpilGames::SETTING_SSL_CAPATH, '/path/to/ssl/ca/');
```

* you can know switch to curl as request handler.

```php
SpilGames::set(SpilGames::SETTING_REQUEST_HANDLER, SpilGames::SETTING_REQUEST_HANDLER_CURL);
```