Code cleanup, Tested with WP 3.9

git-svn-id: https://plugins.svn.wordpress.org/subcategory-list-widget/trunk@905209 b8457f37-d9ea-0310-8a92-e5e31aec5664
Updated readme, bumped version

git-svn-id: https://plugins.svn.wordpress.org/subcategory-list-widget/trunk@905212 b8457f37-d9ea-0310-8a92-e5e31aec5664