PHP requires HEREDOCs to have a newline after them.

See:
http://www.php.net/manual/en/language.types.string.php#language.types.st
ring.syntax.heredoc

> The closing delimiter must also be followed by a newline.
Comment out the setting for the slideshow background.

We’ll readdress this in a subsequent release.
Update the minimum and tested WP versions

Minimum goes to 3.7
Tested goes to 3.8.1