RSS Social Icon validation

[JesseMcL]

Adding the link for the RSS social icon doesn't validate.

quick look at code, and a simple change fixes it.

functions-theme-options.php:

            array(
                'title'       => __( 'RSS Feed', 'responsive-mobile' ),
                'type'        => 'text',
                'id'          => 'rss_uid',
                'description' => __( 'Enter your RSS Feed URL', 'responsive-mobile' ),
                'default'     => '',
                'validate'    => 'checkbox'
            ),

change validate to url and it works as expected.