Delete obsolete files

git-svn-id: https://plugins.svn.wordpress.org/book-review/trunk@911788 b8457f37-d9ea-0310-8a92-e5e31aec5664
Remove obsolete css folder

git-svn-id: https://plugins.svn.wordpress.org/book-review/trunk@911789 b8457f37-d9ea-0310-8a92-e5e31aec5664