Restructure plugin files and folders. Uses a standardized class for the main plugin setup.
Included the actual taxonomies.php file.
Clean up undefined index error.
Overhaul template tags.  Most of them aren't needed anymore.
`echo` argument should be `true` by default.
Better method of getting the current post ID for the related series list.
Make sure we have a post ID.
Overhual widgets.
Rename widget files.
Remove unused admin() method.
Update translation files.
Clean up shortcodes.
Clean up deprecated functions.
Rename template-tags.php to template.php.
Change default order and orderby arguments.
activation() method should not be static.
Update inline docs.
Drop the readme.html file and add the important bits to the readme.txt file.
Add screenshots.
Add readme.md file.