twitter setUserStatus() message and picture support

Twitter api supports tweets with status and **picture** since [v1.1](https://dev.twitter.com/docs/api/1.1/post/statuses/update_with_media).
Like `Facebook::setUserStatus()` and thanks to latest [multipart feature](https://github.com/hybridauth/hybridauth/commit/cd74d9e749b356bf21df05418cbd8aa13c9f8d17) too, we can set a message and picture that will be upload to Twitter with this modified `Twitter::setUserStatus()`.

As simple as:
```php
$twitter = $this->hybridauth->authenticate( "Twitter" );
$twitter->setUserStatus( array( 'message' => 'some message', 'picture' => 'http://..image.jpg' ) );
```

Feel free to merge and use.

best
FA