Update Client.php

[baltazorr]

For correct work of posting shares, I made some changes. Now it's possible to use GET data and POST data in single request. And now it's posible to send XML POST.

POST data sending as 4 parameter in fetch method.

Worked example from real project:

$client = new \Splash\LinkedIn\Client($apiKey, $secretKey);
$client->setAccessToken($token);
$data = "
  <share>
    <content>
        <title>This is title</title>
        <description>This is body</description>
        <submitted-url>http://someurl.com/</submitted-url>
        <submitted-image-url>http://lorempixel.com/400/400/nightlife/</submitted-image-url>
    </content>
    <visibility>
        <code>anyone</code>
    </visibility>
  </share>";
$response = $client->fetch('/v1/people/~/shares', array(), 'POST', $data);