Double encoding of image_link

[pmhou]

When a variant is created, the already processed image_link node is encoded a 2nd time with safeCharEncodeURL() which produces a double encoded string. Namely ' ' (space) becomes %20 which then becomes %2520.

To fix this, I've used urldecode() on the image link string before it is ran through safeCharEncodeURL()

// src/LukeSnowden/GoogleShoppingFeed/Item.php:177
$imageLink = $this->safeCharEncodeURL(urldecode($imageLink);

Fix applied to #20