Fix bug in Share.php

Line no. 11. Erroneous code:

$this->text= urlencode($media);

Change to:

$this->media = urlencode($media);

Problem: The bug overwrites the assignment done in the line above it.

How to replicate: Share on any network, and you can't see the title of the shared page correctly.
Merge pull request #2 from gamergemparq/patch-1

Fix bug in Share.php