Updated URL references
Updated plugin version to 0.2
Updated copyright year.
Added comments for existing functions.  Default the $exclude param to and empty array in the get_random_attached_image() method.
Added 'attachment' param to shortcode attribute defaults
Added support for 'attachment' attribute.
Reformat code
Added 'random image' and 'attachments' tag
Updated 'Tested up to:'  tag to 4.0
Renamed 'Advanced Usage', which gets put into an 'Other Notes' tab on WordPress.org, to 'Frequently Asked Questions'.
Added documentation for new 'attachment' shortcode attribute.
Added change log and upgrade notice for version 0.2.